. . . and so on. The abbreviation et al. (for "and others") is not used in the reference list, regardless of the number of authors, although it can be used in the parenthetical citation of material with three to five authors (after the inital citation, when all are listed) and in all parenthetical citations of material with six or more authors..Reference: Book with More than One Author
Natarajan, R., & Chaturvedi, R. (1983). Geology of the Indian Ocean. Hartford, CT: University of Hartford Press.
Hesen, J., Carpenter, K., Moriber, H., & Milsop, A. (1983).
Computers in the business world. Hartford, CT: Capital Press.