The Publication Manual of the American Psychological Association, 6th ed. (2010) is the authority used by writers in the social sciences and some natural sciences.
Unofficial: CSUF APA Citation Style (PDF) provides a two-page overview of some of the most common citation needs for both the in-text parenthetical documentation and the reference list
Official: APA Frequently Asked Questions and APA Style Help provide a few official examples and additional support from the APA. For the most comprehensive coverage of APA style, including citation rules, please remember to consult the print APA publication manual. Copies are kept at the Reference Desk for in-library use.
Also Available Online:
OWL (Online Writing Lab) at Purdue University. Purdue University's OWL is an excellent source to use for any citation style, inlcuding APA.
Diane Hacker Research and Documentation see Social Sciences for the APA style