Dr. Menegazzi is the editor-in-chief of Prehospital Emergency Care and Dr. Yealy is a deputy editor of Annals of Emergency Medicine. Dr. Reynolds has no relevant financial information or potential conflicts of interest to disclose.
Original Research Contribution
Emergency Medicine Journal Impact Factor and Change Compared to Other Medical and Surgical Specialties
Article first published online: 20 NOV 2012
© 2012 by the Society for Academic Emergency Medicine
Academic Emergency Medicine
Volume 19, Issue 11, pages 1248–1254, November 2012
How to Cite
ACADEMIC EMERGENCY MEDICINE 2012; 19, 1248–1254 © 2012 by the Society for Academic Emergency Medicine
A related commentary appears on page 1297.
- Issue published online: 20 NOV 2012
- Article first published online: 20 NOV 2012
- Manuscript Revised: 2 JUL 2012
- Manuscript Accepted: 2 JUL 2012
- Manuscript Revised: 28 JUN 2012
- Manuscript Revised: 16 MAY 2012
- Manuscript Received: 12 APR 2012
A journal impact factor represents the mean number of citations per article published. Designed as one tool to measure the relative importance of a journal, impact factors are often incorporated into academic evaluation of investigators. The authors sought to determine how impact factors of emergency medicine (EM) journals compare to journals from other medical and surgical specialties and if any change has taken place over time.
The 2010 impact factors and 5-year impact factors for each journal indexed by the Thomson Reuters ISI Web of Knowledge Journal Citation Reports (JCR) were collected, and EM, medical, and surgical specialties were evaluated. The maximum, median, and interquartile range (IQR) of the current impact factor and 5-year impact factor in each journal category were determined, and specialties were ranked according to the summary statistics. The “top three” impact factor journals for each specialty were analyzed, and growth trends from 2001 through 2010 were examined with random effects linear regression.
Data from 2,287 journals in 31 specialties were examined. There were 23 EM journals with a current maximum impact factor of 4.177, median of 1.269, and IQR of 0.400 to 2.176. Of 23 EM journals, 57% had a 5-year impact factor available, with a maximum of 4.531, median of 1.325, and IQR of 0.741 to 2.435. The top three EM journals had a mean standard deviation (±SD) impact factor of 3.801 (±0.621) and median of 4.142 and a mean (±SD) 5-year impact factor of 3.788 (±1.091) and median of 4.297, with a growth trend of 0.211 (95% confidence interval [CI] = 0.177 to 0.245; p < 0.001). By any criterion analyzed, EM journals ranked no higher than 24th among 31 specialties.
Emergency medicine journals rank low in impact factor summary statistics and growth trends among 31 medical and surgical specialties.
El Factor de Impacto de las Revistas de Medicina de Urgencias y Emergencias y su Cambio en Comparación con la de Otras Especialidades Médicas y Quirúrgicas
Un factor de impacto representa el número medio de citaciones por artículo publicado. Se diseñó como una herramienta para cuantificar la importancia relativa de una revista y los factores de impacto se incorporan frecuentemente a la evaluación universitaria de los investigadores. Los autores buscaron determinar los factores de impacto de las revistas de Medicina de Urgencias y Emergencias (MUE), compararlos con revistas de otras especialidades médicas y quirúrgicas y ver si ha tenido lugar algún cambio en el tiempo.
Se recogió el factor de impacto y el factor de impacto de 5 años correspondientes a 2010 para cada revista indexada por Thomson Reuters ISI Web of Knowledge Journal Citation Report de la especialidad de MUE y para las de las especialidades médicas y quirúrgicas. Se determinó el máximo, la mediana y el rango intercuartílico (RIC) del factor de impacto y del factor de impacto de 5 años para cada revista en cada categoría. Las especialidades se clasificaron según los resúmenes estadísticos. Se analizaron las tres mejores revistas en cada especialidad, y la tendencia de crecimiento desde 2001 a 2010 con una regresión lineal con efectos aleatorios.
Se revisaron 2.287 revistas de 31 especialidades. Existen 23 revistas de MUE en la actualidad con un factor de impacto máximo de 4,177, una mediana de 1,269, y un RIC de 0,400 a 2,176. De las 23 revistas de MUE, el 57% tenían disponible un factor de impacto de 5 años, con un máximo de 4,531, una mediana de 1,325 y un RIC de 0,741 a 2,435. Las tres mejores revistas de MUE tenía una media de FI de 3,801 (desviación estándar ± 0,621) y mediana de 4,142; media de FI de 5 años de 3,788 (±1,091), y mediana de 4,297; con una tendencia de crecimiento de 0,211 (IC 95% = 0,177 a 0,245; p < 0,001). Indistintamente del criterio analizado, la clasificación de las revistas de MUE no supera el puesto 24º de las 31 especialidades estudiadas.
Las revistas de MUE se clasifican en un puesto bajo en función del resumen de estadísticas del factor de impacto y existe una tendencia al crecimiento entre las 31 especialidades médicas y quirúrgicas.
Thomson Reuters Journal Citation Reports (JCR) publishes yearly updates of impact factors for journals in the biologic and physical sciences. Before 1991, emergency medicine (EM) journals were classified under anesthesiology, surgery, or miscellaneous. In 1991, the “critical care” category was adopted and EM journals were reclassified into this category. In 1996, the “critical care” category was renamed “emergency medicine and critical care.” Finally in 2000, “emergency medicine” became an independent journal category within JCR.
In 1961, Garfield developed the impact factor, one metric to measure the relative importance of a journal in a field. The impact factor of a journal is the mean number of citations received per paper published in that journal during the 2 preceding years. It is calculated by dividing the number of article citations from the previous 2 years by the total number of articles published by that journal in the same 2 years. All cited articles are eligible for the numerator, whereas eligible articles in the denominator are limited to original papers, reviews, case reports, short papers, proceedings, and other “citable items.” Editorials, letters to the editor, abstracts, and commentaries are excluded from the denominator. JCR also calculates a 5-year impact factor via the same equation, but includes the number of article citations (numerator) and publications (denominator) from the previous 5 years.
The impact factor is used to gauge the prestige of journals in which an author has published, which is often incorporated into decisions about promotion, funding, and tenure.[3, 4] Between 2000 and 2009, the number of EM journals increased 58%, outpacing the growth of every other category of clinical medicine. The impact factors for EM journals also increased, although there has been a widening gap between “high”-impact-factor and “low”-impact-factor EM journals.
Given the increasing impact factors of EM journals in the preceding decade, we sought to determine how both current EM journal impact factors and the rate of growth in the “top-tier” EM journals compare to those from other medical and surgical specialties.
We analyzed all data available in January 2012 from the JCR online database maintained by the Thomson Reuters Web of Knowledge (formerly ISI), including all journals from categories of clinical medicine (surgical and nonsurgical). The JCR identifies journals belonging to each category (i.e., specialty) a priori. We collected data for each journal category, including the number of journals, the yearly impact factor from 2001 through 2010, and the 5-year impact factor from 2006 through 2010 for each journal. No institutional review board approval was sought as the study involved no human subjects.
We calculated the maximum, median, and interquartile range (IQR) for both 2010 and the 5-year (2006–2010) impact factors for journals from JCR-categorized medical and surgical specialties. Given the positively skewed distribution of journal impact factors (Figures 1 and 2), we performed a subgroup analysis on only the “top three” journals from each specialty for 2010 impact factor and 5-year impact factor to reflect the “highest-performing” (i.e., most commonly referenced) journals from each specialty. We did calculate mean ± standard deviation (SD) for the top three journals, since the median value represents only the second-highest impact factor. We then used random-effects linear regression to identify the trend in the mean impact factor for the top three journals in each specialty from 2001 through 2010. We identified the slope of the linear regression as representative of trends, assuming a linear relationship between impact factors and time, and that normality was not strongly violated.
In total, 2,287 journals from 31 journal categories (i.e., medical and surgical specialties) were included in the analysis. We present descriptive statistics (Table 1) and boxplots (Figure 1) for both 2010 and 5-year impact factors for all journals indexed in each journal category. For 23 indexed EM journals, the maximum 2010 impact factor was 4.177, and the median was 1.269 (IQR = 0.400 to 2.176). Of those 23 EM journals, 13 had 5-year impact factors (i.e., had been in publication for ≥ 5 years), with a maximum of 4.531 and median of 1.325 (IQR = 0.741 to 2.435).
|Journal Category||2010 Impact Factor||5-year Impact Factor (2006–2010)|
We present descriptive statistics for both impact factor and 5-year impact factor for the top three journals indexed in each journal category in Table 2. The mean 2010 impact factor was 3.801 (±0.621), and for the purposes of seeing the skew, the median was 4.142. The mean (±SD) 5-year impact factor was 3.788 (±1.091) and median was 4.297.
|Journal Category||2010 Impact Factor||5-year Impact Factor (2006–2010)|
|Maximum||Mean ± SD||Mediana||Maximum||Mean ± SD||Mediana|
|Medicine (general)||53.486||39.043 ± 12.638||33.633||52.363||38.057 ± 12.491||32.498|
|Allergy||9.273||63588 ± 2.552||6.297||8.691||6.092 ± 2.381||5.567|
|Alternative medicine||3.571||3.066 ± 0.463||2.964||4.190||3.499 ± 0.602||3.216|
|Cardiology||14.432||12.926 ± 2.490||14.293||14.932||12.738 ± 2.391||13.091|
|Critical care||10.191||7.147 ± 2.710||6.254||10.019||7.145 ± 2.598||6.453|
|Dermatology||6.270||5.12 ± 1.012||4.750||5.758||4.881 ± 0.785||4.644|
|Gastroenterology||12.032||11.177 ± 0.753||10.885||12.403||11.091 ± 1.290||11.044|
|Geriatrics||9.000||7.594 ± 1.244||7.148||7.978||7.428 ± 0.859||7.868|
|Hematology||14.432||11.498 ± 2.595||10.558||14.932||11.732 ± 2.772||10.190|
|Infectious diseases||16.144||10.396 ± 5.022||8.186||15.470||10.121 ± 4.654||7.898|
|Neurology||21.659||13.879 ± 6.780||10.746||18.277||12.851 ± 4.699||10.143|
|Oncology||94.333||52.814 ± 36.321||37.184||70.245||45.521 ± 21.926||37.881|
|Pediatrics||5.391||4.860 ± 0.719||5.147||5.850||5.457 ± 0.397||5.465|
|Pulmonary||10.191||7.745 ± 2.118||6.525||10.019||7.641 ± 2.073||6.686|
|Rheumatology||9.028||8.210 ± 1.004||8.435||8.579||7.532 ± 1.057||7.551|
|Tropical medicine||4.752||3.694 ± 0.972||3.489||4.849||3.789 ± 0.963||3.551|
|Surgery (general)||7.474||6.540 ± 0.809||6.096||8.998||6.721 ± 2.007||5.983|
|ENT||3.038||2.574 ± 0.411||2.428||3.079||2.869 ± 0.250||2.935|
|Ophthalmology||10.340||6.550 ± 3.302||5.017||10.307||6.682 ± 3.146||5.063|
|Oral surgery||3.933||3.666 ± 0.334||3.773||4.563||4.172 ± 0.533||4.389|
|Orthopedics||3.953||3.697 ± 0.336||3.821||4.801||4.353 ± 0.534||4.495|
|Transplant||6.204||5.682 ± 0.775||6.051||5.983||4.980 ± 0.869||4.508|
|Urology||8.843||7.745 ± 1.447||8.288||7.960||6.701 ± 1.226||6.633|
|Anesthesia||5.486||5.022 ± 0.694||5.355||6.305||5.336 ± 0.935||5.264|
|EM||4.177||3.801 ± 0.621||4.142||4.531||3.788 ± 1.091||4.297|
|OB/GYN||8.755||5.835 ± 2.529||4.392||9.599||6.174 ± 2.973||4.665|
|Pathology||18.778||11.249 ± 3.527||7.695||17.835||9.982 ± 6.801||6.140|
|Psychiatry||15.470||13.004 ± 2.354||12.759||15.618||13.579 ± 1.898||13.253|
|Radiology||7.022||6.343 ± 0.592||6.069||6.821||6.667 ± 0.221||6.766|
|Rehabilitation||3.772||3.065 ± 0.616||2.779||3.951||3.689 ± 0.434||3.927|
|Toxicology||19.238||11.024 ± 7.344||8.741||21.277||11.910 ± 2.178||8.264|
We present trends for the mean impact factor of the top three journals in each journal category from 2001 through 2010 in Table 3. EM journals had a representative slope of 0.211 (95% CI = 0.177 to 0.245; p < 0.001), which signifies a trend of a 0.211 increase in impact factor per year.
|Journal Category||2001||2002||2003||2004||2005||2006||2007||2008||2009||2010||Trend||95% CI||p-value|
|Medicine (general)||19.962||21.240||24.868||28.371||30.463||33.424||35.591||36.715||35.569||39.043||2.157||1.844 to 2.470||<0.001|
|Allergy||4.061||4.556||3.389||4.590||5.113||5.944||5.619||6.511||6.543||6.588||0.340||0.246 to 0.435||<0.001|
|Alternative medicine||0.873||1.319||1.203||1.379||1.405||1.490||2.565||2.444||2.634||3.066||0.235||0.182 to 0.288||<0.001|
|Cardiology||8.701||8.742||9.627||10.556||10.080||10.165||11.177||12.007||12.419||12.926||0.470||0.395 to 0.546||<0.001|
|Critical care||4.465||4.585||5.347||5.174||5.828||6.699||6.660||7.147||7.410||7.147||0.353||0.294 to 0.412||<0.001|
|Dermatology||3.524||3.068||3.567||3.290||3.606||3.683||4.207||4.655||4.882||5.124||0.214||0.155 to 0.274||<0.001|
|Gastroenterology||9.173||9.863||9.582||10.036||9.957||10.635||10.807||11.237||11.032||11.177||0.227||0.182 to 0.272||<0.001|
|Geriatrics||4.221||4.382||4.572||4.864||6.011||6.743||5.942||6.653||6.443||7.594||0.359||0.273 to 0.444||<0.001|
|Hematology||9.668||9.860||10.467||10.772||10.390||10.388||11.124||11.672||11.528||11.498||0.214||0.157 to 0.270||<0.001|
|Infectious diseases||7.363||5.802||5.615||7.572||7.451||7.875||8.281||9.293||10.191||10.396||0.479||0.329 to 0.628||<0.001|
|Neurology||8.181||7.126||7.121||8.213||8.779||8.382||9.183||11.269||12.311||13.879||0.672||0.461 to 0.882||<0.001|
|Oncology||20.455||20.337||28.641||33.065||33.404||39.667||40.691||43.433||47.584||52.814||3.546||3.192 to 3.899||<0.001|
|Pediatrics||3.617||3.487||3.680||3.516||4.074||4.563||4.382||4.651||4.799||4.860||0.172||0.133 to 0.210||<0.001|
|Pulmonary||4.736||4.938||6.200||5.779||6.282||6.744||6.883||7.469||8.030||7.745||0.357||0.298 to 0.416||<0.001|
|Rheumatology||4.548||4.977||5.351||5.356||6.243||6.108||6.129||6.551||6.992||8.210||0.335||0.267 to 0.402||<0.001|
|Tropical medicine||1.773||1.861||2.125||1.978||2.213||2.630||2.374||3.178||3.494||3.694||0.216||0.168 to 0.263||<0.001|
|Surgery (general)||5.442||5.045||5.384||5.301||5.592||6.383||6.058||7.037||6.626||6.540||0.196||0.123 to 0.263||<0.001|
|ENT||2.073||2.004||1.885||2.279||2.335||2.114||2.131||2.485||2.324||2.574||0.055||0.027 to 0.083||<0.001|
|Ophthalmology||4.190||4.151||4.721||4.048||4.961||5.612||5.379||5.103||5.823||6.550||0.239||0.161 to 0.315||0.001|
|Oral surgery||2.921||2.699||2.459||3.095||3.167||4.184||3.482||3.276||3.377||3.666||0.107||0.032 to 0.183||0.005|
|Orthopedics||2.183||2.373||2.602||2.864||3.305||3.100||3.230||3.680||3.640||3.697||0.174||0.144 to 0.205||<0.001|
|Transplant||3.256||3.997||4.509||4.286||4.776||5.148||4.697||5.298||5.235||5.682||0.218||0.163 to 0.274||<0.001|
|Urology||5.225||5.488||5.715||5.263||5.526||5.785||6.315||6.812||7.183||7.745||0.263||0.191 to 0.336||<0.001|
|Anesthesia||3.434||3.624||3.475||3.725||3.676||4.125||4.520||4.985||4.961||5.022||0.206||0.164 to 0.249||<0.001|
|EM||1.747||1.745||1.991||2.115||2.527||2.393||2.824||2.909||3.141||3.801||0.211||0.177 to 0.245||<0.001|
|OB/GYN||3.154||3.393||3.511||3.690||4.511||4.792||5.070||5.385||5.123||5.835||0.303||0.259 to 0.347||<0.001|
|Pathology||7.097||5.786||5.561||5.604||5.493||5.650||5.209||6.267||8.788||11.249||0.369||0.047 to 0.691||0.03|
|Psychiatry||8.381||7.998||7.905||8.588||10.088||11.330||12.001||12.452||13.276||13.004||0.683||0.556 to 0.811||<0.001|
|Radiology||6.109||5.181||5.716||5.413||5.116||5.566||5.876||16.117||6.340||6.343||0.388||−0.245 to 1.022||0.23|
|Rehabilitation||1.289||1.706||1.437||1.967||1.916||2.167||2.911||2.991||3.432||3.065||0.236||0.187 to 0.285||<0.001|
|Toxicology||11.022||10.710||10.727||9.812||10.061||12.024||10.398||11.559||11.770||11.024||0.093||−0.043 to 0.229||0.18|
We present the relative rank of EM journals among the 31 medical and surgical specialties according to impact factor summary statistics in Table 4. By any criterion used (e.g., maximum, mean, or median impact factor; top three subgroup analysis; or 10-year trend), EM journals ranked no higher than 24th among 31 journal categories representing medical/surgical specialties.
|All journals||Top 3|
|Number of journals|
|2010 5-year IF||31st||N/A|
The impact factor is a significant topic for scientific journals, editors, and publishers that garners dozens of articles each year in a wide variety of journals. The impact factor is not without criticism, however, including the very mechanism by which it is calculated. The numerator includes all citations (including editorials, letters, news items, book reviews, errata, meeting abstracts) from either the previous 2 years (impact factor) or the previous 5 years (5-year impact factor), whereas the denominator is restricted to traditional peer-reviewed articles and review articles. A journal that publishes non–peer-reviewed material (e.g., editorials, meeting reports, correspondence, meeting abstracts) can inflate its impact factor over those journals that do not. Additionally, a journal may publish a greater proportion of review articles and/or methods articles that tend to be cited more frequently. More concerning is the possibility that the “citable” items in the denominator may be negotiable between publishers and Thomson Scientific.
There are several historical examples of intentional manipulation of the impact factor. In 2007, Folia Phoniatrica et Logopaedica, an international journal of phoniatrics, speech therapy, and communication pathology, published an editorial in protest of the impact factor, citing all of its articles from 2005 and 2006. As a result, the journal's impact factor increased from 0.66 to 1.44, but it was excluded from the 2008 and 2009 JCR for this overt manipulation. In 2008, Acta Crystallographica Section A, published by the International Union of Crystallography, improved its impact factor from 2.051 to 49.926, higher than both Nature (31.434) and Science (28.103). A single article titled “A short history of SHELX” included a sentence reading, “This paper could serve as a general literature citation when one or more of the open-source SHELX programs (and the Bruker AXS version of SHELXTL) are employed in the course of a crystal-structure determination.” This article alone received over 6,600 citations. The second-most-cited article in Acta Crystallographica Section A had only 28 citations.
Additional criticism levied at the impact factor includes a language bias for international journals that have multiple editions. Joint, Bone, and Spine and Revue du Rhumatisme are English and French editions of the same journal, yet have different citations rates and subsequently different impact factors.
As a result, several other scoring systems have been implemented to evaluate a journal's performance: the eigenfactor, immediacy index, cited half-life, citing half-life, article influence score, h-index, g-index, e-index, and comprehensive citation factor. While detailed analysis of each of these scoring methods is beyond the scope of this article, each attempts to temper the “loopholes” in impact factor calculation and provide alternative means of evaluating a journal's scientific influence.
Historically, there was an intrinsic bias against EM in the derivation of an impact factor. Citation counts in the numerator of the impact factor calculation were derived from a list of “source” journals that did not contain any EM journals. As a result, the only source of citations for EM journals was from journals outside of EM, producing small numerators with relatively constant denominators. That policy has since been changed by ISI: citations counts in the numerator of the impact factor calculation are now derived from all journals indexed in the ISI Web of Knowledge, including EM journals.
Our findings beg the following question: after demonstrable growth in academic EM over the preceding decade, why is the impact factor for EM journals so low compared to journals from other specialties? In other words, why are articles from EM journals cited less frequently than journals from other specialties? The number of studies published that are never cited is threefold higher in EM journals than non-EM journals. Part of the answer may lie in the inherent nature of the specialty and the habits of EM investigators.
Emergency medicine research is by definition multidisciplinary. As such, a sizable portion of EM research is published in non-EM journals. This may be further fueled by a desire of EM investigators to publish in prestigious specialty journals germane to their areas of focus. In fact, up to 30% of original EM literature is published in non-EM journals, which in turn is cited at least twice as often as similar studies published in EM journals. The single strongest predictor of continued citations per year is the impact factor of the original publishing journal, which is much higher in non-EM journals. The journal category “medicine (general)” is a prime example of this. Anecdotally, there is a sizable amount of EM literature that is published in “multispecialty” journals (e.g., JAMA, NEJM, Lancet), which are categorized by JCR as general medicine. This journal category has both the second-highest impact factor and 5-year impact factor for 2010. It would be interesting to tabulate the proportion of articles published in these “multispecialty” journals that are from EM investigators. While publication in these journals raises awareness of EM research, gains an element of prestige for both the investigator and the specialty, and may aide in promotion consideration, it contributes to the low impact factor of EM journals. Furthermore, EM investigators who publish in other specialty journals do not cite EM literature. EM journals provide only 16% of the citations of EM research published in non-EM journals. Taken together, there is a net flow of publications and citations away from EM journals. We hypothesize that this perpetuating cycle of publication and citation keeps the impact of EM journals low compared to other specialties.
Other possible reasons for low impact factors among EM journals (although we suspect less likely) include journal revenue policies resulting in associated fees with manuscript submission or stringent editorial policies in article selection that deter investigators from submitting. Moreover, one may argue that comparing journal impact factors among different specialties is an unfair assessment of scientific prowess. Bornmann et al. claim “the differences in the size of professional communities, the numbers of their indexed journals and type of articles in different fields, and the researchers' differing citing behaviours make the common practice of comparing JIFs [journal impact factors] in different fields … and subfields … non-scientific and absolutely unacceptable.”
Whether the specialty should be concerned about its journals' impact factors and what steps could be taken to increase them are debatable questions, but one must consider if the impact factor is a meaningful measure of academic performance. It is the most widely accepted quantitative and objective method for evaluating journals. Although many promotion committees recognize the flaws in impact factor when considering the productivity of investigators, some institutions may rely on both total and mean publication impact factor for faculty promotion. It may be investigators at these institutions who are most likely to submit original work to non-EM journals.
The journal categories that have outpaced EM journals in impact factor increases may very well be publishing high-quality science that is simply cited more often. Alternatively, they may be publishing a large amount of items that are excluded from the denominator, but still attract numerous citations, which artificially inflates impact factor. Conversely, journals that lag behind EM may not be publishing “high-yield” articles for continued citations. Nabil and Samman discovered that between 2007 and 2008, case reports alone comprised 31% of publications in the four major English-language oral and maxillofacial surgery journals, which had a mean citation rate of less than 1. Only 7.2% of these case reports received more than five citations, of which 30% were also case reports. They noted that the publication of these case reports negatively affected journal impact factor, which correlated directly with the percentage of case reports published.
We used the JCR database to gather data, which is an English-language database and has an American publication bias, even though European journals (mostly German, French, and Spanish) are included.[19, 20] The contribution of other non–English-language or non-American journals is unknown using our approach.
Emergency medicine journals rank low in impact factor summary statistics among 31 medical and surgical specialties. This may be due to the inherently multidisciplinary nature of the specialty as well as publication and citation practices of EM investigators.
- 1Thomson Reuters. The Thomson Reuters Impact Factor. Available at: http://thomsonreuters.com/products_services/science/free/essays/impact_factor. Accessed Aug 24, 2012.
- 8Thomson Reuters. Journal Citation Reports Notices. Available at: http://admin-apps.webofknowledge.com/JCR/static_html/notices/notices.htm. Accessed Aug 24, 2012.
- 9Thomson Reuters. What does it mean to be #2 in Impact? Available at: http://community.thomsonreuters.com/t5/Citation-Impact-Center/What-does-it-mean-to-be-2-in-Impact/ba-p/11386. Accessed Oct 17, 2012.
- 12Impact factor and other standardized measures of journal citation: a perspective. Indian J Dent Res. 2009; 20:81–5., .
- 14Comprehensive citation factor: a novel method in ranking medical journals. Eur J Dermatol. 2011; 21:495–500., , .