The increasing employment of bibliometric measures for assessing, describing, and mapping science inevitably leads to the increasing need for a citation theory constituting a theoretical frame for both citation analysis and the description of citers' behavior. In this article a theoretical model, encompassing both normative and constructivist approaches, is suggested. The conceptualization of scientific communities as autopoietic systems, the components of which are communicative events, allows us to observe the reproductive function of citations conceived as codes and media of scientific communication. Citations, thanks to their constraining and enabling properties, constitute the engine of the structuration process ensuring the reproduction of scientific communities. By referring to Giddens' structuration theory, Luhmann's theory about social systems as communicative networks, Merton's “sociology of science” and his conceptualizations about the functions of citations, as well as Small's proposal about citations as concept-symbols, a sociologically integrated approach to scientometrics is proposed.