If there are two authors for a publication you wish to cite, you cite them this way:
(Stone & Burns 1956)
If there are more than two authors, then you can probably (ask your TA, if you want to be sure) get away with using the name of the senior author--the one whose name appears first in an article, or under whose name a book is cataloged--followed by "et al." which means "and others." In this example, Smith is the first-listed author; do not use the alphabetical order of authors' names in deciding what names to use in a citation. Smith, Burns, Garcia, and Sullivan 1980:87 can be cited as
(Smith et al. 1980:87)
American Anthropologist, a major journal, now prohibits the use of et al. in the text, because it is undemocratic. I recommend the use of et al. --not because I'm undemocratic, but because it seems to me that a citation with three or more names interferes with the ease of reading the text, and I do not believe many instructors would object to this use of et al. in term papers. In your reference list, you must use the names of all the authors. Unless you are undemocratic. Democratic example:
(Smith, Burns, Garcia & Sullivan 1980: 87)