Gaya APA

Marx, M, H., Cronan-Hillix, W, A. (1989). Systems and theories in psychology (4th ed). New York: McGraw-Hill.

Gaya MLA

Marx, Melvin, H.., Cronan-Hillix, William, A.. "Systems and theories in psychology". 4th ed New York: McGraw-Hill, 1989. Text.