The American Political Science Association uses a variation of the Chicago Manual of Style citation system. It concentrates on formats important to political science, with special attention given to documents produced within the United States government. It provides a pragmatic and simple way to reference publications in a variety of formats.
The most recent citation style guide (2006) for the American Political Science Association is predicated upon the the publication of the 16th edition of the Chicago Manual of Style. Most of the citation style guidelines are based on the Chicago Style.
APSA relies on an author-date system (as used in Chicago Style), and in APSA, parenthetical references within the text [also known as in-text citation and parenthetical citation] direct readers to the reference list.
Source: High Point University - http://guides.highpoint.edu/c.php?g=85880&p=552109