The Purdue Owl (Online Writing Lab) is a useful resource and reference tool for questions about formatting and grammar.
MLA guidelines are
here.
APA format guidelines are
here.
For sources with multiple authors:
For a source with two authors, list the authors’ last names in the text or in the parenthetical citation:
Best and Marcus argue that one should read a text for what it says on its surface, rather than looking for some hidden meaning (9).
The authors claim that surface reading looks at what is “evident, perceptible, apprehensible in texts” (Best and Marcus 9).
For a source with three or more authors, list only the first author’s last name, and replace the additional names with et al.
According to Franck, et al, “Current agricultural policies in the U.S. are contributing to the poor health of Americans” (327).
The authors claim that one cause of obesity in the United States is government-funded farm subsidies (Franck, et al. 327).
For sources with no author available:
When a source has no known author, use a shortened title of the work instead of an author name. Place the title in quotation marks if it's a short work (such as an article) or italicize it if it's a longer work (e.g. plays, books, television shows, entire Web sites) and provide a page number.