MLA Style Guide is typically used in English, Science, and Geography disciplines.
APA Style Guide is typically used in the Humanities and Social Sciences disciplines.
Chicago Style Guide is typically used in Business, History, and Fine Arts disciplines.
Purdue University maintains an excellent writing website with thorough resources on three of the most popular style guides used in academic circles: APA, Chicago, and MLA. Visit the OWL Purdue website to explore them fully.