Shaughnessy, J. J., & Zechmeister, E. B. (1997). Research methods in psychology (4th ed.). McGraw-Hill.

Shaughnessy, John J., and Eugene B. Zechmeister. Research Methods in Psychology. 4th ed. New York: McGraw-Hill, 1997.

Shaughnessy, John J., and Eugene B. Zechmeister. Research Methods in Psychology. 4th ed. McGraw-Hill, 1997.