Collaboration and Internationalization of SMEs: Insights and Recommendations from a Systematic Review

This paper performs a systematic literature review of the undeniably diverse – and somewhat fragmented – current state of research on the collaborations and internationalization of small and medium‐sized enterprises (SMEs). We analyze key works and synthesize them into a framework that conceptually maps key antecedents, mediators, and moderators that influence the internationalization of SMEs. In addition, we highlight limitations of the literature, most notably in terms of theoretical fragmentation; extant theories are deployed and illustrated but rarely extended in a manner that significantly informs subsequent work. At an applied (but related) level, we argue the need for supplementary work that explores the distinct stages of internationalization – and the scope and scale of this process – rather than assuming closure around particular events. With this, we highlight the need for more rigorous and empirically informed explorations of contextual effects that take account of the consequences of developments in the global economic ecosystem.


Introduction
A considerable body of research has investigated how small and medium-sized enterprises (SMEs) recognize and take advantage of opportunities embedded in international markets. Indeed, in most national contexts, most internationalization activities are undertaken by such enterprises (D'Angelo et al. 2016;Gashi et al. 2014). While the internationalization of SMEs is examined from a range of different perspectives, a significant body of literature focuses on the role of networks and collaborations.
Again, many scholars have highlighted the effect of size and ownership (as organizational characteristics) on the nature and dynamics of firms' internationalization processes (Fernández and Nieto 2006;Sadler-Smith et al. 2003;Zhang et al. 2016). However, it is notable that no unified scientific definition exists of the precise constitution of an SME (Bocconcelli et al. 2018;Motwani et al. 2006). Key criteria include the number of employees, assets, and scale of annual turnover, or a mixture of these factors. This issue becomes even more complicated when such criteria are applied differently in different economic regions (e.g. Europe vs. the USA) and sectors (e.g. service vs. manufacturing) (Bocconcelli et al. 2018). Despite these discrepancies, it is agreed that SMEs are subject to common constraining attributes, such as limited human, financial, and informational resources (Rogers 1990;Welsh and White 1981), a lack of legitimacy abroad (Sapienza et al. 2006), and limits in short-term resilience (Bradley et al. 2006). Hence, an SME's weak resource base is likely to make the decision to enter into international markets particularly challenging. Indeed, a significant amount of research has been devoted to understanding how 428 Zahoor et al. SMEs can internationalize in the face of such difficulties.
A prominent stream in this literature proposes that interorganizational collaboration may help alleviate these challenges (Chetty and Holm 2000;Oviatt and McDougall 1994;Puthusserry et al. 2018). Such collaborative linkages help SMEs overcome their resource limitations (Coviello 2006;Lu et al. 2010), establish legitimacy and credibility, and develop bespoke capabilities for international entry at lower risks (Zhou et al. 2007). In other words, collaborative internationalization may represent a major source of competitive advantage for internationalizing SMEs.
Notwithstanding the considerable progress made in the collaborative internationalization field, two important limitations remain. First, research on this topic is still fragmented, with a diverse evidence base (Lindstrand and Hånell 2017). Existing research on collaborative internationalization in SMEs may be roughly divided into two broad areas of inquiry, one focusing on antecedents of collaborative internationalization and the other on its mediators and moderators. Studies focusing on antecedents have explored the relationship of firm and organizational characteristics with internationalization outcomes (Belso-Martínez 2006;Ciravegna et al. 2014b). However, research on mediators/moderators has only recently begun investigating the mediators and moderators between antecedents and internationalization outcomes (Felzensztein et al. 2019;Qian et al. 2018;Nakos et al. 2019), leaving significant scope for further investigation in this respect, especially given the diversity within this literature. The second limitation concerns the lack of clarity on the ways in which SMEs attain different internationalization outcomes (Ciravegna et al. 2014b). To date, a brief review of network research in the area of entrepreneurship can be found in the work of Jones et al. (2011), and a broader review of the role of networks in early internationalizing firms in the work of Bembom and Schwens (2018). However, these studies offer limited explanations of the variation of SMEs' internationalization outcomes 1 (Ciravegna et al. 2014b). 1 The heterogeneous structure of SMEs means that a certain number of them decide to internationalize from inception; these are termed born-global (Rennie 1993) or international new ventures . Others, however, known as born-again global SMEs (Bell et al. 2001), internationalize rapidly but operate after a few years in the domestic market; yet others, termed traditional SMEs (Graves and Thomas 2008), internationalize late, in reaction Against this backdrop, this paper aims to review, analyze, and critically synthesize the current state of research into SMEs' collaborative internationalization, using the analysis to identify gaps in the literature and articulate potential areas for future studies. In doing so, we make two important contributions. First, we map the field of collaborative internationalization in SMEs by analyzing and categorizing the existing literature into specific interrelated themes. Second, we synthesize the latter to develop an overarching framework that specifies the key antecedents, mediators, moderators, and outcomes, explaining the connections between them. Furthermore, we deploy this framework as a platform to discuss two key directions for future research.
The remainder of the paper is organized into four sections. The next section summarizes our methodology; it is followed by a synthesis of key trends, theories, and perspectives on factors influencing internationalization in SMEs. The penultimate section discusses the findings and presents directions for future research. Our conclusions are reported in the last section.

Methodology
To ensure a rigorous systematic literature review (SLR) of published work on collaborative internationalization in SMEs, we adopted Denyer and Tranfield's (2009) multi-step review approach to assemble and review the relevant literature. The four-step iterative process (as outlined in Figure 1) ensures study robustness and rigor by eliminating the subjectivity in data collection and analysis found in traditional literature reviews (Cacciotti and Hayton 2015;Tatli and Özbilgin 2012). These four steps involve defining the review questions, establishing the scope and boundaries of the review, study identification, the screening and selection process, and analysis and synthesis.

Defining the review question
The literature on collaborative internationalization and SMEs emerged almost 20 years ago (Chetty and Holm 2000). So far, a number of questions have been addressed, including collaborative internationalization value, the organizational arrangements adopted in building relationships, and contingency factors to a particular event. To ensure an exhaustive review, we have included all these types of SME. (e.g. drivers, facilitators, inhibitors) that may constrain or enhance the effectiveness of SMEs in establishing collaborative linkages for internationalization. However, the literature remains fragmented (Mesquita and Lazzarini 2008;Stoian et al. 2017), limiting our understanding of the true nature of this relationship and its underpinning dynamics. Therefore, in this SLR, we seek to identify, categorize, and analyze relevant strands of the extant literature, aim-ing to build an overarching framework that can provide new insights into the relationship between collaboration and internationalization, highlighting the fundamental components, potentials, and remaining gaps. To this end, we set our investigation across four key questions: 2. What are the theories that underpin research on SMEs' collaborative internationalization? 3. What are the various factors that can influence the essence and outcomes of SMEs' collaborative internationalization? 4. What are the implications for future research suggested by our findings?

Establishing the scope and boundaries of the review
To build a comprehensive database of collaborative internationalization literature, we defined a number of different criteria for the inclusion and exclusion of studies (see Appendix S1). We set our timeframe to include peer-reviewed papers published between 1994 and 2019, choosing 1994 as our starting year because the first journal article that discussed the collaborative internationalization of SMEs was published in that year (Bell 1995;McDougall et al. 1994). Next, we defined the key conceptual boundaries of the investigated phenomenon (Denyer et al. 2008). More specifically, we established the boundary conditions for three key terms: collaboration, internationalization, and SMEs. First, the term collaboration is defined as the interaction, relationship, and ties existing between a small firm and other organizations (Huggins 2010). 2 To be consistent with previous review papers (Agostini and Nosella 2017;Street and Cameron 2007), we considered strategic alliances and networks as two common forms of collaboration. The second term, internationalization, is conceptualized as the process of increasing involvement in international markets through the various forms of foreign direct investment and/or exporting (Welch and Luostarinen 1993). Using this definition, we were able to capture the distinct dimensions of internationalization, such as internationalization speed and internationalization success.
Our search revealed different approaches for defining and conceptualizing SMEs (our final term), indicating the absence of common consent (Nolan and Garavan 2016). As summarized in Table 1, a group of studies defined SMEs according to number 2 Two salient forms of collaboration are strategic alliances and networks. While the former refers to 'short or long-term voluntary relations between organizations concerning one or more areas of activity-such as market entry, skill acquisition, or technological exchange' (Dacin et al. 2007, p. 170), the latter concerns a set of nodes that link a group of organizations together (Gulati 1998). of employees (Galkina and Chetty 2015;Zucchella et al. 2007), while others based their definitions on revenues (Ciravegna et al. 2014b;Montoro-Sanchez et al. 2018), or encompassed both number of employees and revenue (Ibeh and Kasem 2011;Zhou et al. 2007). There is also variation in categorizing firms according to number of employees; European SMEs can have up to 250 employees (European Commission 2003), widely different from the US and Chinese standards of up to 500 employees reported in 2010 by the US Small Business Administration (SBA) and Zhou et al. (2007). This may not merely reflect arbitrary categorizations; it may also reflect variations in the regulatory environment and the relative support available to firms of different sizes within specific markets. To address the challenge of insufficient definitional clarity, we followed Örtenblad's (2010) advice to use an interpretive approach that 'attempts to understand what is done and/or written under the headings of the concepts (i.e., the labels), regardless of whether this is in accordance with any exact definitions of the particular labels or not' (p. 446). Therefore, we set out to understand what is meant by the label SME by examining each article in depth and looking to see how SMEs had been defined. Importantly, this approach enabled us to focus on the implications of the smallness of these firms. Consequently, in this study, we define an SME as an independent, resource-constrained firm that is labeled as a small firm, SME, international new venture, or new venture (see Group string 3, Appendix S2, for the full list of terms we have incorporated in this study). By adopting a comprehensive approach, we captured a wider range of the literature than we would have done if a single definition had been used. Indeed, such an approach was also taken by previous SLR papers (Ansari et al. 2010;Klang et al. 2014;Nolan and Garavan 2016).
After establishing our conceptual boundaries (i.e. the three concepts of collaboration, internationalization, and SMEs), we developed a series of keywords. Variation in the terminology used to capture the concepts made it necessary to incorporate a commensurate variation in search terms. Following a brainstorming exercise and an initial search of articles, we identified 23 keywords related to the three concepts and merged them to build a combined search string, as shown in Appendix S2.
work appearing in books, book chapters, and conference papers, as well as predatory journals (Stumbitz et al. 2018). Importantly, excluding books and other forms of publication was necessary to avoid double counting, as the bulk of rigorous scholarly work is likely to appear first in peer-reviewed journal articles (Ankrah and Omar 2015); however, we recognize that this may have resulted in a small handful of potentially seminal texts being excluded. In addition, articles published in recognized academic journals are regarded as credible because they go through rigorous peer-review processes and thus enhance the quality of a SLR (Hilligoss and Rieh 2008;Newbert 2007).
In response to calls for interdisciplinary research in management studies (Jones and Gatrell 2014), we undertook article searches using a wide range of electronic databases, including EBSCOhost Business Source Complete, Elsevier Science Direct, Web of Science (ISI), ABI Inform, Google Scholar, SAGE Journals, and Wiley Online Library. To reduce the risk of excluding key articles because of the rigidity of our review process, we further conducted an independent search in Google Scholar to confirm the results of the main search (Mol et al. 2015).

Study identification and the screening and selecting process
This step aims to identify, screen, and select suitable studies to help answer our review questions.
First, the initial search was conducted in various databases and by using the Google Scholar search engine with the keyword combinations shown in Appendix S2 to identify potential articles published between 1994 and 2019. This process identified 1,941 articles as potentially relevant for analysis. The identified articles were imported into the bibliographic software EndNote X9.
Second, using the Endnote X9 Find Duplicates command, we reduced the 1,941 identified studies to 1,273. Next, we checked our initial sample against quality screening criteria, as outlined in Appendix S1. More specifically, a focus on articles with methodological and theoretical rigor means that basic quality criteria are met (Matthews and Marzec 2012;Nguyen et al. 2016). We therefore chose studies from higher-ranked journals. We referred to journals as high-grade if they were ranked at Grades 3, 4, or 4* in the Chartered Association of Business Schools (CABS) academic journals list (Baldacchino et al. 2015). The CABS list provides an international ranking of journals and is widely recommended in previous review articles (Soundararajan et al. 2018). This process reduced the number to 376 studies for the selection stage of the review.
Finally, we scrutinized the 376 studies against the fit-for-purpose criteria (see Appendix S1 for details). In general, fit-for-purpose criteria concern the validation of studies to meet the intended purpose of the review (Boaz and Ashby 2003). As this study's objective was to identify, categorize, and synthesize literature on the ways in which collaboration leads to an internationalization process of SMEs, our fit-for-purpose criteria for including studies from the 376 papers were to include studies: (1) where collaboration is explicitly linked to internationalization of SMEs, and (2) whose context concerns SMEs.
We reviewed the abstracts of the studies at this stage. In a number of cases, however, it was difficult to clearly identify the study aim, theory, research method, and findings; to shed light on these issues, the introductions or conclusions (or both) of these studies were examined (Thorpe et al. 2005). Eventually, this process produced the 105 papers that constituted our final sample. This number is adequate for the systematic review, and several prior studies have used similar numbers of articles (Baldacchino et al. 2015;Klotz et al. 2013;Lahiri 2016).

Analysis and synthesis
To avoid an undue emphasis on one study over others (Dixon-Woods et al. 2006;Mulrow and Cook 1998;Tranfield et al. 2003), a transparent process of synthesis is required to investigate and combine findings from the 105 studies. Narrative synthesis is regarded as an effective way to identify the story underpinning a disparate and fragmented body of evidence, as it gives researchers the flexibility to develop themes that bring coherence to those data (Bailey et al. 2015;Nijmeijer et al. 2014). SMEs' collaborative internationalization may be considered an established research stream . Guided by Popay et al.'s (2006) recommendations, we summarize our approach to narrative synthesis in the next paragraph.
We started by analyzing each study of the final sample to identify the context of SMEs, theoretical perspective, study's geographical location, sector, industry, and methodology. We designed a worksheet to record this information, which we carefully scrutinized for potential errors (Bailey et al. 2015).
This worksheet allowed us to create a map of the field in terms of density, frequency, and emerging patterns (MacPherson and Holt 2007). Next, using Nvivo 10, we deployed in-depth, line-by-line coding to identify and categorize the concepts involved in the study, as well as the links between concepts, enabling the results to provide useful insights for future research. However, this task proved challenging because of the complexity of the field in terms of theoretical perspectives, level of analysis, and research methodologies. We therefore tried to provide a suitable framework that would fit with our review questions and integrate disparate results logically. As an initial approach to this task, we opted to apply the antecedents-mediators-outcomes (AMO) framework (McGrath 1964) to identify, categorize, and synthesize the review findings. In principle, the AMO framework allows researchers to study the complexity of the middle ground that connects antecedents to outcomes (Ghezzi et al. 2017;Klotz et al. 2013). Several studies show that the AMO framework is robust for the purpose of integrating findings and framing future research endeavors (Agostini and Nosella 2017;Street and Cameron 2007). We therefore initially synthesized existing research by deductively coding and clustering the articles' findings within the AMO framework (Parmigiani and King 2019). For example, looking at the studies, collaboration characteristics were grouped under antecedents. Next, lineby-line analysis was conducted to inductively evaluate the articles and segment the findings into related themes and conceptual constructs. For example, governance mechanism was identified as a collaboration activity after a close inspection of the study by Odlin and Benson-Rea (2017). The inductive approach also allowed us to extend the AMO framework by identifying a range of moderating factors for the collaborative internationalization linkage. Thus, two complementary approaches (deductive and inductive) allowed us to check for completeness in antecedents, mediators, moderators, and outcomes (Fischer et al. 2017).

Results
This section presents the results of our analysis of the key trends in empirical research, theories underpinning the research, outcomes, antecedents, mediators, and moderators of SMEs' collaborative internationalization.

Key trends in SMEs' collaborative internationalization literature
The distribution of articles on SMEs' collaborative internationalization in 25 different journals is shown in Appendix S3. The published journals span fields including Entrepreneurship and Small Business Management, International Business and Area Studies, Marketing, General Management, Social Sciences, Strategy, and Innovation. The first article on collaborative internationalization appeared in 1994 in the Journal of Business Venturing (i.e. McDougall et al. 1994). Since then, the number of articles has consistently increased (see Figure 2). Two-thirds of the articles (67%) in our review sample were published in the last decade. We also noted a recent upsurge, as 36% of articles in the sample were published between 2015 and 2019. However, few studies appear in the leading international business and marketing journals (as evident in Appendix S3); this is surprising given the increasing interest in the topic of collaborative internationalization (Idris and Saridakis 2018).
As predicted, researchers included in our SLR sample used a wide range of terms for SMEs, along with varying size distributions (see Table 1). In addition, we noticed heterogeneity in the methodological and contextual orientation of sample studies. In terms of methodological orientation, as set out in Appendix S4, most of the selected studies (n = 90/105) were empirical, while review papers (n = 8/105) and conceptual papers (n = 7/105) contributed about 8% and 7% of the total sample, respectively. With respect to empirical articles, collaborative internationalization research is moving from qualitative phenomenological studies toward quantitative theory-based studies (Martineau and Pastoriza 2016). More quantitative (n = 52) than qualitative studies (n = 31) were represented, along with a few mixed-method studies (n = 7). The quantitative designs employed include cross-sectional surveys (n = 40) (e.g. Lu et al. 2010;Mesquita and Lazzarini 2008), personal interviews (n = 4) (e.g. Ferreras-Méndez et al. 2019), lagged surveys (n = 2) (e.g. Elango and Pattnaik 2007), and longitudinal data (n = 6) (e.g. Eberhard and Craig 2013; Idris and Saridakis 2018). Qualitative designs include single case studies (Chetty and Stangl 2010;Francioni et al. 2017), multiple case studies (e.g. Galkina and Chetty 2015;Ojala 2009), and longitudinal case studies (Chetty and Holm 2000). Interestingly, 42% of the qualitative studies, but only 24% of the quantitative studies, were published before early 2007; the trend shifted from qualitative toward quantitative after that date. This could be explained by a shift of era toward statistical analysis and big data in international business research (Delios 2017). The majority of articles in the Journal of International Business Studies (n = 5), Entrepreneurship, Theory and Practice (n = 2), Journal of Small Business Management (n = 7), and Journal of World Business (n = 10) were quantitative. In contrast, the International Business Review had an equal balance of quantitative (n = 12) and qualitative methods (n = 10).
Our review sample shows heterogeneity in contextual orientation (i.e. geographical context and industrial context); see Appendix S5. In terms of geographical context, our review sample covers 37 countries in seven different regions, as shown in Appendix S5. In terms of diversity of countries in each study, most of the papers conducted research in one country (n = 76), but some examined two (n = 3), three (n = 5), or more than three countries (n = 6). While most of the research on SMEs' collaborative internationalization has focused on countries in Europe (n = 61), Oceania (n = 21), and America (n = 17), limited focus remained on developing countries (n = 18). The first article on a developing country (China) appeared in 2001 in the International Business Journal (Ling-yee and Ogunmokun 2001). After 6 years, another article was published on the internationalization of Chinese SMEs in the Journal of International Business Studies (Zhou et al. 2007). After that, there was a growing trend of research on SMEs' collaborative internationalization in developing countries, but there was replication of context in published studies. We also investigated the correlation between geographic location and method of study. The findings revealed that the mixedmethod studies were conducted in many developed countries, particularly New Zealand and various European countries (e.g. Hughes et al. 2019;Loane and Bel 2006). Similarly, most of the quantitative studies focused on developed countries (n = 40/50), with a handful of studies (n = 10/50) carried out in developing and emerging countries. In contrast, qualitative studies focused equally on developed and developing countries. In terms of industrial context, there was substantial bias toward manufacturing industry (n = 64), particularly high-technology industry (n = 25). A number of studies considered the services industry (n = 2), a mix of manufacturing and service industries (n = 9), and multiple industries (n = 15) as their empirical settings. Despite the changes in the structure of developed countries (Alexandersson 2015;Cimoli and Katz 2003), there is a lack of research focus on the retail and media industries.
In addition to the trends demonstrated above, the analysis provides important insights into the usage of theory. We identified four common theories to explain collaborative internationalization in SMEs (see Table 2).
The most popular approach proved to be network theory (n = 28). According to this, markets are depicted as systems of social and professional  Mesquita and Lazzarini (2008) relationships among and between customers, suppliers, and competitors (Liu et al. 2017;Martineau and Pastoriza 2016); informed by this, a number of studies explore the informal side of collaborative internationalization (Pinho and Prange 2016). Specifically, network-based studies show that SMEs can employ social capital to learn about conditions in the host country (Idris and Saridakis 2018); they share the risks of failure and trepidation associated with entry into foreign markets (Manolova et al. 2010;Naudé et al. 2014).
The second most frequently used theoretical framework is the resource-based view (RBV) (n = 24). Proponents of the RBV suggest that, when applied in the context of collaborative internationalization, small firms' internal resources/capabilities (such as returning entrepreneurs, technological resources, and financial resources) facilitate the effective utilization of collaboration for international performance (cf. Barney 1991;Brouthers et al. 2015;Catanzaro et al. 2018). In addition, scholars demonstrate that networks are considered a strategic resource, bringing value to the firm in the form of international opportunity exploitation and the expedition of international operations Tang 2011). Together, the unique configuration between the internal resources of SMEs and their networks can become distinctive firm-specific capabilities, sources for creating competitive advantage, that lead to superior performance in the international market.
The third prominent theory is international entrepreneurship theory (n = 12). As this suggests, a combination of innovative, proactive, and riskseeking behaviors leads some new ventures to start their international operations from inception McDougall 1994, 2005); these behaviors encompass a temporal element (being in the right place at the right time), a relational element (the unplanned building of social networks), and an analytical element (the ability to establish connections between actual data and ideas) (Ciravegna et al. 2014a;Crick and Spence 2005). For example, Felzensztein et al. (2015) found that entrepreneurs use their personal networks to scan for opportunities in new international markets. Overall, using international entrepreneurship theory, previous research suggests that the entrepreneurial characteristics of managers and the entrepreneurial behavior of the firm allow SMEs to rapidly internationalize and achieve international growth (Cavusgil and Knight 2015;Knight and Cavusgil 2004).
Finally, the Uppsala model of internationalization is a framework scarcely used by previous research (n = 6). It conceives internationalization as an incremental process whereby a firm gradually increases its international involvement by increasing relevant knowledge (Johanson and Vahlne 1977). The core assumption behind this model is the interplay of two elements: the development of international operationsrelated knowledge and the increasing propensity of firms to commit resources to international operations (Elango and Pattnaik 2007). In other words, exposure to international markets allows small firms to build knowledge about foreign markets, thereby gaining further increases in international market involvement (Odlin and Benson-Rea 2017). Thus, the core idea of studies using the Uppsala model is that the development of objective knowledge (acquired easily from home markets) and that of experiential knowledge (acquired through engagement in international operations) of international markets are both prerequisites for international operations.
In contrast to the focus on a single theory (as discussed above), researchers have utilized multiple theoretical perspectives arguing that a single perspective can limit the potential to fully explain and understand the complexity of SMEs' collaborative internationalization linkages (Matanda and Freeman 2009). Combinations of multiple perspectives can therefore provide complementary insights at different levels (Frynas and Stephens 2015). For instance, by integrating the RBV with network theory, scholars suggest that network resources facilitate joint value creation for the internationalization of SMEs (Boehe 2013;Matanda and Freeman 2009). Similarly, combining insights from the RBV, the knowledge-based view, and the relational view, Haahti et al. (2005) argued that an SME's ability to build collaborative relationships with other firms is a crucial capability to acquire knowledge about foreign markets, which, in turn, leads the firm toward internationalization.
In summary, our scrutiny of the main theoretical perspectives deployed suggests two important issues. First, we note certain similarities between the four theoretical perspectives. For example, the central argument underlying network theory, RBV, international entrepreneurship theory, and the Uppsala model is that the competitive advantage of firms is rooted in their unique constellation of resources: organizational, physical, human, and network positions (Johanson and Vahlne 2009;Nahapiet and Ghoshal 1998). We thus argue that there is potential to develop a holistic theoretical approach, where collaborative internationalization is understood to result from complementarities between factors and resources. Second, we observed the 'reactive' theoretical trend in collaborative internationalization literature. Although research into SMEs' collaborative internationalization has developed and evolved into an independent research area, it has been carried out, up to now, through replication of the theories used in the context of large firms. There is a need for 'active,' theoretical, trend-setting research on SMEs' collaborative internationalization; it starts with the small-business perspective and is tailored to the idiosyncrasies of the small business as a central unit of analysis (Soundararajan et al. 2018).

SMEs' collaborative internationalization literature: A critical narrative
This section develops a narrative interpretation of the literature on SMEs' collaborative internationalization; it is based on the analysis we have undertaken and summarized in Figure 3, which provides a multilevel framework of the collaborative internationalization phenomenon in terms of its varying antecedents, mediators (i.e. collaboration activity), moderators, and outcomes.
SMEs' collaborative internationalization: outcomes. These are the consequences of antecedents and collaboration activity. While research on the outcomes of collaborative internationalization has received significant scholarly attention, this construct has been conceptualized differently in the literature. As such, analysis of the studies in this field shows three distinct yet interrelated outcome categories: organizational outcomes, internationalization outcomes, and performance outcomes. Subsequent discussion will show the existence of important links connecting these three outcome categories, as illustrated in Figure 3.
The first category, organizational outcomes, relates to the direct advantages that SMEs attain through collaboration and can drive SMEs' internationalization and overall performance outcomes (Stoian et al. 2017). In examining organizational outcomes, prior research has focused on two key advantages: collective efficiency and international market knowledge. Collective efficiency is defined as the competitive advantage derived from combining SMEs' resources and capabilities (Lages et al. 2009;Mesquita and Lazzarini 2008). For instance, research shows that engagement in networks develops the ability to absorb and exploit external knowledge residing with partners (Ferreras-Méndez et al. 2019;Tolstoy and Agndal 2010), which, in turn, enhances SMEs' innovation capacity (Nassimbeni 2001;Stoian et al. 2017). Likewise, collaborative relationships enable joint planning of production schedules and constant monitoring of production processes, both of which will enhance the manufacturing productivity of small firms and their ability to target the global market (Mesquita and Lazzarini 2008). In contrast, acquiring international market knowledge (as an organizational outcome) has received significant attention, with several studies showing that SMEs can offset their limited knowledge of foreign markets by developing new market knowledge bases through collaboration (Cesinger et al. 2016;Haahti et al. 2005;Stoian et al. 2017).
Second, internationalization outcomes concern the development of SMEs' economic activities beyond their national boundaries. In this respect, our analysis has yielded four different sub-outcomes that SMEs may attain through collaboration: international market entry, international diversification, international success, and international growth. First among these, international market entry refers to the speed with which SMEs enter international markets. While some small firms internationalize from inception (bornglobal firms) as a result of the availability of resources from local networks (Crick 2009;Gassmann and Keupp 2007), others internationalize long after being established, as a result of foreign market knowledge acquisition from international network partners and their involvement in international networks (Andersson et al. 2013;Ibeh and Kasem 2011). As the interest in international market entry research grows, scholars have recently come to view it as a multi-dimensional concept (i.e. speed, scope, and extent) . In particular, post-entry internationalization speed has emerged as a new phenomenon (Sadeghi et al. 2018) that needs further empirical attention. Second, international diversification can be defined as the number of markets into which a small firm has entered (Zhang et al. 2016). While this sub-outcome captures the international expansion scope of SMEs (Prashantham et al. 2019), it has received limited scholarly attention (Felzensztein et al. 2015). Third, international success encompasses a firm's achievement of international objectives in terms of sales, market share, profitability (Karami and Tang   and Tang 2019), and strategic advantage of superior design, quality, and customer service in international markets (Ling-yee and Ogunmokun 2001). Finally, international growth has been utilized as a way of understanding the international development of SMEs over time, being conceptualized as an increase in foreign sales (Prashantham and Dhanaraj 2010;Zhou et al. 2010), increase in the number of countries served (Coviello and Munro 1997), and in-crease in the number of employees engaged in foreign activities (Presutti et al. 2016) within a specific timeframe.
Finally, performance outcomes relate to firms' overall profitability and sales growth. Despite the importance of performance outcomes and their potential to be influenced by the SMEs' collaboration activity (Kiss et al. 2012;Martineau and Pastoriza 2016), they have received little scholarly attention.  Zhou et al. (2007) have shown that guanxi networks can positively affect firms' overall profitability. Similarly, Hessels and Parker (2013) found that informal collaborations promote firms' overall growth as well as their international success. There is scant evidence of the importance of internationalization to firms' profitability and growth (Love and Roper 2015), but some mixed empirical findings exist (Hessels and Parker 2013;Zhou et al. 2007).
Stream 1: Antecedents-outcomes (direct effect). Our analysis shows that researchers have paid close attention to the conditions (i.e. antecedents) that influence the SMEs' outcomes (as in Figure 3). This focus has identified organizational, relational, and context-specific factors that not only exist in large numbers but also overlap in many aspects (Belso-Martínez 2006;Francioni et al. 2017). However, in our analysis, we were able to untangle this complexity by clustering the factors into a number of analytical levels, including individual, firm, network, and environmental levels (see Figure 4).
Individual-level antecedents concern the managerial attributes that can influence SMEs' internationalization potentials. As evident in Figure 4, findings consistently show that managers' personal attributes -such as education level (Hughes et al. 2019), international experience (Filatotchev et al. 2009), work experience (Prashantham and Dhanaraj 2010), knowledge of foreign languages (Zucchella et al. 2007), managerial commitment (Ibeh and Kasem 2011;Kalinic and Forza 2012), and managerial vision and learning orientation (Weerawardena et al. 2007) -are related to SMEs' international success (Alvarez 2004) and international speed (Zucchella et al. 2007). Again, entrepreneurs' international experience and knowledge allow born-global SMEs to start operations from the beginning, unlike their later counterparts (Hughes et al. 2019;Sinkovics et al. 2018).
Firm-level antecedents comprise the inherent properties of SMEs that play roles in influencing internationalization outcomes. Such factors include firm dynamics, resources, and strategic advantages. As summarized in Figure 4, work exploring the impact of firm dynamics identified characteristics of SMEs (including firm size, age, ownership, and research & development [R&D] intensity) as predictors of internationalization outcomes. Regarding size, research found that an increase in firm size is likely to persuade managers to leverage learning fully from their experiences and promote international success (Filatotchev et al. 2009; Villena Manzanares 2019). Firm age is also an important determinant of internationalization, because older firms have more resources and therefore a higher propensity to internationalize (Catanzaro et al. 2018;Chang and Webster 2018). In terms of ownership, one stream of research suggests that foreign ownership provides an international link to increased opportunities in international markets (Chang and Webster 2018). The other stream argues that ownership by a local entrepreneur increases the international success of firms (Chang and Webster 2018;Elango and Pattnaik 2007). Research also suggests that simultaneous consideration of internal and external ownership allows the mitigation of managers' risk-averse behaviors and promotes international scope and success (George et al. 2005). R&D promotes international success by improving the firm's ability to adapt products to local market conditions and take advantage of new market opportunities (Filatotchev et al. 2009;Keeble et al. 1998).
In addition to firm profile, our review identified the role of resources as a firm-level antecedent, revealing the effect of resource stocks. Prior findings demonstrate that technological resources help small firms to offer innovative products and maintain customer relationships, resulting in more internationalization opportunities (Kim and Hemmert 2016). Similarly, financial resources stimulate entry into foreign markets because they allow small firms to invest in the relevant technology early in their development and invest in quality management to develop relationships with external partners (Crick and Spence 2005;Freeman et al. 2006). A related cluster of work considered knowledge resources and suggested that availability of product and market knowledge allows a small firm to enter in distant foreign markets (D'Angelo et al. 2013;Kim and Hemmert 2016). Beyond the resources, we identified firms' strategic direction, comprising entrepreneurial orientation (EO) and organizational strategies, as an antecedent of internationalization outcomes (Weerawardena et al. 2007). EO is a widely studied antecedent in the literature (Karami and Tang 2019; Villena Manzanares 2019); researchers argue that entrepreneurial firms are able to gain foreign market knowledge (Karami and Tang 2019) that is conducive to international success (Acosta et al. 2018), international speed (Kalinic and Forza 2012), and international growth . Considering strategic advantages, a limited number of studies suggest that focalization strategy (i.e. positioning in a global market niche) allows the effective choice of foreign market and thereby enables fast international growth (Cannone and Ughetto 2014;Zucchella et al. 2007). Likewise, some studies suggest that differentiation of products allows a small firm to avoid large competitors and rapidly enter for-eign markets (Elango and Pattnaik 2007;Odlin and Benson-Rea 2017).
Network-level antecedents relate to the preformation attributes and configurations of external relationships that may promote SMEs' internationalization (as in Figure 3). On this premise, researchers have extensively studied a number of factors (as summarized in Figure 4), which we categorized as collaboration type, collaboration characteristics, and social capital.
First, scholars found that collaboration type is the determinant of organizational outcomes (Mesquita and Lazzarini 2008;Stoian et al. 2017) and internationalization outcomes (Bell 1995;Cerrato et al. 2016). Second, a group of studies considered collaboration characteristics as network-level antecedents. A high degree of collaboration intensity helps to build the legitimacy and trust needed to accumulate large amounts of knowledge (Boehe 2013;Cesinger et al. 2016). Furthermore, proximity to the network center influences a small firm's ability to access new resources and gain market information on its road toward internationalization (Coviello 2006;Odlin and Benson-Rea 2017).
Researchers have also explored the relevance of social capital, referring to resources embedded in a social structure of relationships; these are accessed by purposive action (Presutti et al. 2016). Work exploring the impact of social capital on outcomes has focused not only on interorganizational social capital Presutti et al. 2016) but also on international and market-specific social capital (Lindstrand et al. 2011); different features of social capital can mold the dynamics and outcomes of internationalization (Prashantham and Dhanaraj 2010;Puthusserry et al. 2020).
Finally, environmental-level antecedents have received limited attention (see Figure 4). For example, institutional support (e.g. export promotion programs) can enable SMEs to realize international success due to the availability of finance and favorable exporting policies (Alvarez 2004;Chetty and Holm 2000;Lu et al. 2010).
Stream 2: Antecedents-activity-outcomes (mediation and moderating effects). Our review reveals that some studies have explored the factors or mechanisms that mediate the relationship between antecedents and outcomes (the central block in Figure 3), as well as the factors that moderate some of the relationships associated with SMEs' collaborative internationalization (as shown in Figure 3).
For mediating mechanisms, we used the term collaboration activity to describe the management of post-formation dependencies between partners to capitalize on antecedents for desired outcomes (e.g. Qian et al. 2018). Collaboration activity allows a small firm to take advantage of an alliance, once it is formed and running, by exploiting antecedents in order to realize outcomes. Importantly, analyzing the literature in this respect has yielded three aspects, as shown in Figure 5: governance mechanisms, collaboration management capability (CMC), and knowledge spillover.
Governance mechanisms, which relate to the actions and practices that enhance joint actions in established relationships, represent a key collaboration activity and consist of commitment, cooperation, and power (Bradley et al. 2006;Chen 2003;Tang 2011). Commitment, defined as a partner's intention to remain in the relationship (Tang 2011), helps to cultivate longer-lasting relationships (Ling-yee and Ogunmokun 2001). Qian et al. (2018) highlight both the impact of environmental issues on internationalization and the role of strategic alliances. Cooperation refers to a process whereby partners coordinate their activities to achieve superordinate goals (Haahti et al. 2005); it is a crucial governance mechanism that facilitates exchange relationships. Bradley et al. (2006) argue that cooperation is critical during the initial stage of the relationship, while commitment becomes important later on. Nakos et al. (2019) highlight how alliances mediate the effects of institutional context and environment. Taking cooperation as a mediating mechanism, Matanda and Freeman (2009) conclude that environmental volatility requires a high degree of cooperation in order to respond to market changes, ultimately promoting international growth; this includes taking imbalanced power between partners into account (Odlin and Benson-Rea 2017).
Collaboration management capability (CMC) helps to exploit the antecedents for internationalization outcomes (Khan and Lew 2018;Pinho and Prange 2016). It refers to the ability of a firm to maintain long-lasting relationships by using a set of routines, skills, or both (Al-Tabbaa et al. 2019; Khalid

Figure 5. Stream 2 linking antecedents-activity-outcomes (mediation effects). [Colour figure can be viewed at wileyonlinelibrary.com]
and Bhatti 2015). First, interorganizational learning substitutes for a small firm's lack of international experience and helps to transfer knowledge among collaboration partners for international success (Bruneel et al. 2010). Second, interorganizational coordination (coordination of partner activities and resources) acts as a mediator for SMEs to utilize interorganizational networks for international success (Ling-yee and Ogunmokun 2001; Lu et al. 2010;Tolstoy and Agndal 2010). Third, the availability of information about customers' needs, market opportunities, and business partners' needs leads to information acquisition; as a mediating mechanism, this allows SMEs to exploit interorganizational networks for international success and thus achieve international growth .
Knowledge spillover, a process whereby recipient firms exploit knowledge originally developed by another firm, is an important collaboration activity between horizontal collaboration and international growth of SMEs. Prior studies show that knowledge spillover allows SMEs to gain technological knowledge from horizontal partners that leads to international growth (Del Giudice et al. 2019). By the same token, Ferreras-Méndez et al. (2019) posit that absorptive capacity allows small firms to understand how unfamiliar knowledge introduced by their partner firms fits with their existing knowledge, with the combination resulting in international success.
Moderators. Our review identified a number of moderating factors in the relationship between antecedents and outcomes (see Figure 6). We grouped them as firm-level, network-level, and environmental-level moderators.
Firm-level moderators have been considered by several studies. One set has explored how firm size moderates the impact of key antecedents on outcomes. Using a case study approach, Chetty and Stangl (2010) suggested that SMEs growing in size are better able to rapidly internationalize by taking advantage of collaboration partners. Idris and Saridakis (2018) found that firm size positively moderates the relationship between interpersonal networks and international success. Eberhard and Craig (2013) focused on family ownership as a moderator and found that the relationship between networking (interorganizational and interpersonal) and SMEs' international success is weaker for family firms than for non-family firms, due to autocratic and paternalistic family firm culture. Likewise, Zhang et al. (2016) considered firm ownership (i.e. state-owned or non-state-owned) as a moderator; they argued that

. Stream 2 linking antecedents-moderators-outcomes (moderating effects). [Colour figure can be viewed at wileyonlinelibrary.com]
state-owned firms need more interorganizational networks for innovativeness and international diversification because of their lack of access to local business opportunities. Two studies have considered the moderating role of firm age. While Manolova et al. (2010) found that the association of interpersonal and interorganizational networking with international success would decrease with the age of the firm, Chetty and Stangl (2010) suggest that older firms are more likely to use collaborative relations to rapidly enter geographically distant markets. The differences in the findings of these studies might be due to different dependent variables (i.e. international success and international speed). Recently, researchers have considered innovation as a moderator. For example, Musteen et al. (2014a) suggested and confirmed a positive relationship between international collaborations and rapid internationalization of those SMEs that place greater emphasis on technological innovation. Similarly, Hollender et al. (2017) found support for the hypothesis that the relationship between local collaboration and international performance is positively moderated by product innovation.
Network-level moderators have been relatively little examined in extant research. Boehe (2013) found that distance from the network center negatively moderates the relationship between collaboration intensity and international success. The more distant the firms from the cluster center, the weaker the relationship between collaborative intensity and international success becomes. These findings are corroborated by Presutti et al. (2016), who suggest that distance (geographical and psychological) between an SME and its foreign customers reduces the positive effects of social capital evolution on the firm's international success. Relational ties are also considered as an important moderating variable. For instance, Yu et al. (2011) focused on network cohesion (i.e. more ties among a venture's alliance partners) and found that it increases the positive effect of marketing knowledge from foreign and domestic partners on international success, but that this effect decreases over time. In a similar vein, Zhang et al. (2016) considered the moderating effect of business and political ties for the relationship between EO and SMEs' international diversification. They found that these ties allow entrepreneurial small firms to maintain legitimacy in international markets and reduce the cost associated with foreign entry into multiple markets. Prashantham and Birkinshaw (2015) found that host-country ties negatively moderate the relationship between collaboration relationships and international success because collaboration and hostcountry ties act as substitutes.
Environmental-level moderators have received very limited scholarly attention. In this regard, Musteen et al. (2014a) found that environmental hostility in the domestic market positively moderates the relationship between the expected international networks and the likelihood of early internationalization. The unfavorable domestic market conditions encourage small firms to use international contacts to rapidly enter international markets.
Overall, it is clear that the random use of moderating variables has made it difficult to identify a regular pattern among them. In addition, not a single study explicitly highlighted the moderators at the firm level. Thus, there is considerable scope to investigate these moderators in future studies.

Discussion and directions for future research development
The overarching aim of this study is to systematically analyze and synthesize empirical and conceptual research that focuses on the collaborative internationalization of SMEs. In fulfilling this aim, we mapped the progress of the field over the past three decades, discussed the various theories and conceptual perspectives applied so far (as summarized in Figure 4), and presented an integrative framework that identifies the different aspects of these interorganizational relationships and explicates the linkages between them (as illustrated in Figure 3). In this section, we discuss the implications of our findings and identify gaps and avenues for future research, focusing on the three key themes of theory, content, and methodology.

Directions for theory development and utilization
Our review revealed that not all studies have made strong or systematic usage of theory to underpin their empirical investigations and enhance the credibility of the field. A lack of attention to theory means that relationships between collaboration and internationalization have been somewhat cursory, operating at the broad conceptual level rather than seeking to impart theoretical depth. A limited number of theories appear -mainly network theory, RBV, international entrepreneurship, and the Uppsala model -but there are few attempts to promote theoretical syntheses or significantly develop and extend them. Theoretical synthesis is distinct from the juxtaposition of theo-ries or the presentation of two theories in a single paper. Rather, it seeks to explain how two theories are not only compatible but also complementary; in other words, their integration adds more to understanding than their component parts do separately. At the heart of network theorizing is the relative density and nature of interrelationships. While some strands of institutional theory suggest that networks serve as a substitute for effective institutional mediation (Schneider 2018), others suggest that denser networks are encountered in contexts where institutions foster collaboration (Jackson and Deeg 2019). Again, if networks encompass imbalances in power relations, they also reflect variations in resource endowments, which in turn may relate to internal resources within the organization (Ludwig et al. 2018).
Once more, comparative institutional theory highlights national and sub-national variations in its ability to engender and sustain tangible and intangible intraorganizational resources (Jackson and Deeg 2019). Entrepreneurial behavior may represent another form of social action that is molded and remolded by structure (cf. Lane and Wood 2009), but it also represents strategic responses to physical and economic environmental challenges. While internationalization may be incremental and follow the accumulation of knowledge (as per the Uppsala model), such accumulation is also bound to reflect the operation of networks and what may be engendered through the operation of formal social structures (cf. Jackson and Deeg 2019). This is not to suggest that the most promising future theoretical direction is the sphere of comparative institutional analysis; much international entrepreneurial behavior is episodic and may reflect localized solutions to individual and small-scale challenges and opportunities, rather than wider structural forces. However, these challenges and opportunities may provide an important element in any theoretical synthesis, especially if the regional and international variations in the ability to engender and sustain transnational enterprise are considered. This would suggest a closer emphasis on the interconnectedness of things might be in order (Wood et al. 2020) rather than on events unfolding in distinct spheres. This is particularly important, as much of the research on the topic focuses on immediate or short-term outcomes; a longer view, taking account of structure, resource dynamics, and choices -and the ways in which they impact on each other -might shed further light on the challenges of sustaining international enterprise over time, as well as on the drivers of future upscaling or retreat.
Moreover, future studies could pay more attention to the dark side of relational ties, as most of the existing studies on networks provide a positive view of networks and the internationalization of SMEs. There is scope to draw insights from the ecosystems and service-dominant logic and examine how resource sharing and recombination of resources for value creation takes place within the collaborative networks of internationalizing SMEs (Caridà et al. 2018;Lusch 2010, 2017).
In addition to the above issues, collaborative internationalization could benefit from incorporating the micro-foundation perspective (Barney and Felin 2013). Recent research shows that adopting this perspective may improve the understanding of micro-actions and interactions of lower-level organizational members and their effects in different domains. These include the evolution of multinational business enterprise (Coviello et al. 2017), network change and stability (Kaartemo et al. 2019), the sharing of international knowledge (Foss and Pedersen 2019), and learning in international joint ventures (Park and Harris 2014). Focusing on the individuallevel factors can offer new insights into the effect of the characteristics of SMEs' decision-makers, chief executives, and owners on the process by which the firms use alliances to internationalize. For instance, there is a need to understand how the motivations of SMEs' owners or founders can shape the risk-taking approach underpinning the internationalization decisions of SMEs (Chittoor et al. 2019). Also, the micro-foundation perspective is useful in helping to understand how SMEs evolve interorganizational social capital in international business relations (Puthusserry et al. 2020); the perspective can thus complement the network theory by guiding scholarly attempts to decode the network development process for internationalization (cf. Vahlne and Johanson 2020). For example, there is a need to understand the micro-processes and dynamics of different networks (e.g. local and international) that SMEs form for internationalization. In this respect, several researchers have highlighted the role of actors in interorganizational relationships (e.g. Al-Tabbaa and Ankrah 2019). Prashantham and Birkinshaw (2019) explicitly stressed the need to explore 'the influence of actors' (un)reliability in fostering equilibrium states versus tensions and exploring further the governance of cooperative relationships' (p. 12). There is also a need to examine the role of the board of directors' networks and their impact on the SMEs' post-internationalization speed.
In contrast, using the relational view (Dyer and Singh 1998;Lavie 2006) and its recent development advantage (Dyer et al. 2018) can push the knowledge boundaries in this respect. This theory maintains that interfirm relationships can be a source of competitive advantage (Dyer et al. 2018;Lavie 2006), suggesting a framework comprising four interrelated mechanisms for creating value and achieving relational rents: complementary resources and capabilities, relation-specific assets, knowledge-sharing routines, and effective governance. Therefore, using this theory can provide new insights into the collaborative internationalization of SMEs, as existing theories emphasize only one or two of these mechanisms. For instance, while the RBV focuses on the role of firms' resources and capabilities in driving alliance performance (e.g. Brouthers et al. 2015), the network theory emphasizes relational learning and network characteristics as key success factors for alliance (Stoian et al. 2017). The simultaneous consideration of the four mechanisms can open the door for a new wave of research that answers important questions: How and when should SMEs allocate alliance-specific resources to enhance the process of relational learning? To what extent can the resource interdependence between partners influence the alliance governance structure? How and under what conditions can SMEs benefit from the four mechanisms ex-post alliance? How can the characteristics of effective governance (i.e. commitment, cooperation, power) influence the shape of SMEs' knowledge-sharing routines (e.g. the essence of their absorptive capacity)? Indeed, the conceptual connection between the four mechanisms, as rationalized by the theory, can provide systematic guidance when seeking to address these inquiries. Moreover, in our view, the relational view fits well with the SME domain because this view has been extended to explain how and why resource-limited firms are achieving competitive advantage (Zhang et al. 2016). Furthermore, relational and network approaches can be integrated with global value chains' perspectives in order to understand the opportunities and barriers SMEs face during the pre-and post-internationalization stages (e.g. Su et al. 2020).

Directions for content development
In preceding sections, we have outlined key strands in the relevant literature; these highlight valuable extensions to the knowledge base as well as limitations, gaps, and opportunities for future empirical inquiry, which are potentially informed by the theoretical agenda we have outlined. This section addresses the second theme in the discussion, namely content, which focuses on the factors, dimensions, and mechanisms that have been investigated in the collaborative internationalization literature. We drew on the findings (as summarized in our framework) and their implications to identify research gaps and suggest future research opportunities.
First, the analysis shows that few studies captured in our review have considered individual-or environmental-level antecedents of new ventures. In this regard, we suggest two key areas -environmental issues and firm-level antecedents -which are of particular interest.
Environmental issues -encompassing institutions and physical resources -in both country of origin and domicile are likely to enable, encourage, or restrain cross-border ventures. While most studies take account of context, this is often presented in a manner that either explains some peculiarity or other, or, more commonly, as background detail in describing universal phenomena. This would suggest the need for more detailed consideration of real contextual dynamics and legacies as well as for more systematic, evidence-based reflections on what is specific to a particular setting, which aspects of this are of wider potential interest, and what reflects broader issues and forces. Again, such reflections could be better informed by theoretical syntheses that take account of social structures, material and less substantive resource endowments, and choices. This would also help to account for the scale and scope of international diversification and explain why some players spread their international efforts widely while others do not. Many emerging and developing economies have implemented pro-market reforms, thus it would be interesting to investigate how such reforms shape the local and international collaboration strategies of SMEs, as well as the impact of such collaborations on SMEs' internationalization patterns.
Firm-level antecedents -namely firm size and firm ownership -are under-investigated in the examined literature. Most of the reviewed studies perceive SMEs as a unitary object of analysis; they do not distinguish between small and medium-sized enterprises. Attempts at doing so have been made in European countries, emphasizing that small and medium-sized enterprises differ in terms of resource base, leading them to take different approaches (more or less structured) toward networks and markets (Coltorti et al. 2013;Simon 2009;Snaith and Walker 2002). However, many SME-focused collaborative internationalization studies have made little or no distinction between small and medium-sized enterprises. Further research could accord more attention to the effect of smallness, recognizing that such firms encompass a wide spectrum of heterogeneous enterprises (e.g. micro, small, medium), all varying in their resources, managerial capabilities, and organizational knowledge. Specific approaches are much needed to fully understand how the smallness effect really influences the internationalization preference mode as well as performance. To complement the previous argument, it is notable that there is very little reflection, if any, on how collaborative internationalization looks for SMEs with different management and ownership structures. Sadler-Smith et al.'s (2003) study provides useful insights in this respect by highlighting the effect of managerial behavior and entrepreneurial style on small firms' performance. As such, a handful of studies (e.g. Georgelli et al. 2000;Hodgetts and Kuratko 2001) have indicated that firm ownership matters to collaborative internationalization. For instance, small firms with entrepreneurial leadership have a greater propensity to take risks and innovate than do those led by owners with a managerial mindset: owners such as these might focus on securing income, whereas entrepreneurial leaders would be driven by profitability and growth. Furthermore, evidence suggests that the internationalization behavior of family-owned firms distinguishes them from non-family ownership, such that family businesses confer strategic advantageincluding flexibility and speed in decision-making, supportive family culture, and a long-term orientation -all of which can assist collaborative internationalization (Eberhard and Craig 2013). Researchers, therefore, can build on these insights to investigate a number of critical issues: How can ownership attributes (e.g. entrepreneurial vs. managerial owners) determine possible collaboration patterns for internationalization? What are the differences between family-and non-family-owned SMEs in their perspectives toward collaborative internationalization? How does collaboration help female-owned SMEs achieve internationalization? Are ownermanaged SMEs more or less oriented than independent manager-managed firms toward the adoption of collaboration practices for internationalization? In what ways? Although each manager's education level and experience were recognized as important factors (e.g. Hughes et al. 2019), the understanding of leadership style remained limited. In moving forward, research can consider the role of leadership styles, reputation, and characteristics, as well as the relevance of different leadership styles in specific settings, which might affect the organizational and internationalization outcomes (Khan and Lew 2018).
Second, a theme running through the literature captured by this review is that of the initial episodes of internationalization; many studies make assessments of internationalization based on its relative success at a particular point in time. Only limited attention has been paid to what happens to SMEs' internationalization efforts subsequently -post-entry growth or survival (Khan and Lew 2018;Masiello and Izzo 2019). Again,  noticed recently that speed is a complex, multidimensional concept made up of three elements: entry speed, scope speed, and commitment speed. Future research could fruitfully incorporate this and understand how different antecedents influence the different speed elements, such as preand post-internationalization, and how and at what stage actual performance is best captured. Moreover, post-formation contingencies may alter the basis of alliances (Robson et al. 2019). A greater focus on dynamic forces is required to manage post-formation dependencies and realize the benefits for firm performance; this would help to shed further light on the phenomenon (Dyer et al. 2018). In fact, structural changes in the global economic ecosystem -such as those that preceded and followed the 2008 crisis (Sinkovics et al. 2018) -may have remolded the scale and scope of SMEs' internationalization. In contexts of crisis, both formal and informal collaboration may enhance the survival of SMEs and provide access to external financing for internationalization (Presutti et al. 2016;St-Pierre et al. 2018). In a focus on firm-level dynamics, there has been a tendency to neglect the impact of interrelated 'world-changing' or challenging events such as the COVID-19 pandemic; the same could be true for changes in the global physical environment and the extent to which climate change may drive entrepreneurs to diversify their efforts across national boundaries.
Finally, our sample included studies that investigate collaboration activity as a mediating mechanism in the relationship between antecedents and outcomes, as in Figure 5. Interestingly, our analysis shows that this stream has received less scholarly attention than the first (the direct effect), and thus offers substantial avenues for new research.
Primarily, uncovering the underlying collaboration activities through which antecedents influence outcomes does not go far enough. We found that the research related to collaboration activity starts with the governance mechanism as a safeguarding process to utilize the networks for internationalization outcomes of SMEs (Chetty and Holm 2000;Matanda and Freeman 2009). It then builds on the capabilities view that internally focused capabilities and collaboration management capability (CMC) are the basis for capitalizing on networks for internationalization (Ferreras-Méndez et al. 2019;Khalid and Bhatti 2015). However, future research must go further and capture additional mediating mechanisms. To be specific, while researchers propose the relevance of effectuation and the causal approach to network building for SMEs' internationalization (Kurt and Kurt 2020), we know little about how the quality and intensity of networks, as well as entrepreneurs' personality characteristics, can influence the effectual and causal approach to network building for internationalization . A connected area of research is to consider opportunity creation and discovery, learning-bydoing, and internationalization of R&D as potential collaboration activities through which effectuation and causal networks lead to outcomes (Del Giudice et al. 2019). Future research is required to understand partner type and mode of collaboration, and how these influence SMEs' internationalization processes across developed, emerging, and developing markets.
Furthermore, to date, research has failed to account for the moderating factors related to the mediation effect. Going forward, therefore, we see much scope for research on the factors that shape the relationships between antecedents, collaboration activity, and outcomes. In particular, organizationaland environmental-level moderating factors should be considered. In terms of organizational factors, understanding how organizational structures and processes moderate the outcomes of collaboration activity is promising (St-Pierre et al. 2018). This is because collaboration activity has been associated with commitment and cost, both of which lead small firms to consider mechanisms (e.g. organizational structure, ownership, and domestic strategy) for successful organizational and internationalization outcomes (Yu et al. 2011;Zhang et al. 2016).

Directions for methodology development
Our review discovered some important trends in collaborative internationalization research; it also highlighted that there is little agreement among researchers on methodological and contextual orientations. Building on these trends, we suggest a number of future research directions.
First, the existing body of collaborative internationalization research is deficient in terms of countries covered, with very limited studies in developing countries, particularly those in Africa. Also, there is significant bias toward single-country studies, given the complexity in data availability and participants' access. We therefore advocate the undertaking of collaborative research to develop multinational comparative studies because there are differences in the institutional characteristics of, for example, developing, emerging, and developed countries (Ceipek et al. 2019).
Second, we found evidence of significant method bias in previous studies. For example, many of the empirical studies in our review are quantitative in nature. Unsurprisingly, quantitative studies rely heavily on cross-sectional data and frequently ignore longitudinal data. In order to understand the complexities of collaborative internationalization and determine causal linkages, it is important to examine longitudinal data. In addition, given the paucity of research on collaboration activity, we suggest in-depth qualitative comparative studies to fully explore the indirect effects of collaboration and the ways in which it interacts with other forms of influence. The use of qualitative research will also help build theories by bringing together the concerns of practitioners and the field knowledge of scholars.
Third, in order to understand the context of SMEs, researchers need to be more systematic in the types of industries selected in their samples; our review revealed little justification of these choices. Our sample studies showed a great diversity in the manufacturing industries, but some settings have certainly not received sufficient attention, such as retail, professional services, and non-profit firms. These sectors are among the largest contributors to the deepening of capital in world economies, but they face significant challenges in knowledge acquisition and protection (Higón et al. 2010). These sectors are thus ripe for investigating the collaborative internationalization relationship. Researchers also need to be more specific in categorizing SMEs (Bocconcelli et al. 2018). Our review reveals great diversity in the numbers of employees in different countries, which suggests that the results of previous studies have the potential to be highly idiosyncratic. This implies that more scholarly efforts are required to establish con-sistency in the literature with regard to the definition of SMEs.

Limitations
Despite its rich insights, the current study is not free from limitations. First, to ensure the quality of our review, we took the decision to focus only on peer-reviewed articles. In consequence, we excluded books, conference papers, working papers, and theses. Given the number of selected studies (n = 105), our focus on peer-reviewed articles has provided a comprehensive picture of the collaborative internationalization literature. Nonetheless, it must be acknowledged that there might be publication bias (Harrison et al. 2014). Second, we used the AMO framework to integrate the findings of previous studies. Although this framework has served our analysis well and its use is in line with other reviews (Niesten and Stefan 2019;Street and Cameron 2007), there may be some limitations in coding the studies. However, as we used an iterative inductive-deductive approach, we are confident that we identified the most important themes in the SME collaborative internationalization literature. Third, we did not extend the scope of our review to include papers relating to large firms. We took this decision for pragmatic reasons, in that the number of studies to be evaluated would have been vast, and for theoretical reasons, as SMEs are different from their large counterparts. The inclusion of large firms would not have allowed the applicability of the review to small firms. However, there is scope for future reviews to evaluate the work on SMEs and large firms together. Such studies could pay more attention to age, size, temporal dimensions, and their impact on internationalization.

Conclusion
Collaborative internationalization research in the context of SMEs is expanding. At the same time, the study highlighted not only a number of common themes (in terms of shared foci on specific processes and outcomes) but also theoretical fragmentation. Using this as a basis, we make a case for theoretical synthesis, incorporating institutional structures and entrepreneurial actions as well as resources (material and immaterial) and physical environmental issues. This synthesis takes fuller account of the interconnections between these phenomena and firm internationalization. Again, while the study reveals a wide cross-section of research in different national contexts, specific regions -such as Africa -remain relatively neglected. National contexts are often presented in a manner that either takes the form of incidental background information in describing seemingly universal phenomena or something that is peculiarly unique. This would suggest a need for deeper, more evidence-based reflections as to which phenomena captured by specific studies are generalizable and which are not, as well as more rigorous cases for the scholarly comparative worth of the latter. Once more, there is clearly a need to tell a fuller story of the process, its antecedents, and outcomes; one that is less temporally bounded or assumes closure around some specific outcome or other. This is not to suggest that research needs to be open-ended; rather, it highlights the need for work to explore different stages and phases of the SME internationalization process, its scale and geographical scope, and its relative sustainability. The present systematic review was conceived to provide a holistic picture of collaborative internationalization research, seeking to establish further research avenues. We hope that this paper will inspire SME internationalization research and enhance the understanding of collaborative internationalization in the management literature.