American Psychological Association (APA) style is an academic format specified in The Publication Manual of the American Psychological Association, a style guide that offers academic authors guidance on various subjects for the submission of papers to the publications of APA.
The MLA Style Manual and Guide to Scholarly Publishing (2008) is the third edition of The MLA Style Manual, first published by the Modern Language Association of America in 1985. It is an academic style guide widely used in the United States, Canada, and other countries, providing guidelines for writing and documentation of research in the humanities, especially in English studies; the study of other modern languages and literatures, including comparative literature; literary criticism; media studies; cultural studies; and related disciplines (but not disciplines like history, philosophy, and theology, which follow The Chicago Manual of Style).
The Chicago Manual of Style (abbreviated in writing as CMS or CMOS [the version used on its website], or verbally as Chicago) is a style guide for American English published since 1906 by the University of Chicago Press. Its sixteen editions have prescribed writing and citation styles widely used in publishing. It is "one of the most widely used and respected style guides in the United States."