The basic format is author last name and page number (Green 49).
*** If there isn't a page number, include only the author's names. If there is no author (singular or group), put title as author.
For two authors: (Green & Brown 49)
For three or more authors (Green et al. 49)
Multiple works in one citation: (Gass and Varonis 143; Thomas 24).
Group/ organization as author: (American Psychological Association 123)
Author names in the narrative: Gass and Varonis found that the most important element in comprehending non-native speech is familiarity with the topic (163).