APA style is set forth in Publication Manual of the American Psychological Association, 4th ed. (1994). The APA reference style and similar styles are the most commonly used citation formats. The Council of Biology Editors, for example, recommends two citation systems, an in-text number system (see Council of Biology Editors Citation-Sequence System) and a parenthetical name-date system that closely resembles the APA style. Similarly, the Chicago Manual of Style recommends the parenthetical author-date system as "generally most economical in space, in time (for author, editor, and typesetter) and in cost (to publisher and public)--in short, the most practical" (1993, p. 640).
Guidelines for APA Parenthetical Citation