The University of Iowa's Writing Center offers links to a variety of citation resources: http://writingcenter.uiowa.edu/resources

Purdue's Online Writing Lab (OWL) has the most comprehensive descriptions of MLA, APA, and Chicago: https://owl.english.purdue.edu/media/pdf/20110928111055_949.pdf

The Chicago Manual of Style is available online through the UI Library at http://www.chicagomanualofstyle.org/16/contents.html. Log in with your HawkID and password.