Gaya APA

Wallen, N, E., Fraenkel, J, R. (1991). Educational research : a guide to the proces . New York: Mc-Graw-Hill.

Gaya MLA

Wallen, Norman, E.., Fraenkel, Jack, R.. "Educational research : a guide to the proces". New York: Mc-Graw-Hill, 1991. Text.