APA Style originated in 1929, when a group of psychologists, anthropologists, and business managers convened and sought to establish a simple set of procedures, or style rules, that would codify the many components of scientific writing to increase the ease of reading comprehension.
As with other editorial styles, APA Style consists of rules or guidelines that a publisher observes to ensure clear and consistent presentation of written material. It concerns uniform use of such elements as
The official guide to APA style is found in the 6th edition of the Publication Manual of the American Psychological association. Periodically the APA official website adds updates and corrections. In addition, your professor may have his or her own specific style requirements -- so it is important to communicate with your professor about his or her style requirements.
In addition to the official style guide, there are additional resources online: