Cooper, D. R., & Schindler, P. S. (2003). Business research methods (8th ed.). McGraw-Hill.

Cooper, Donald R., and Pamela S. Schindler. Business Research Methods. 8th ed. Boston: McGraw-Hill, 2003.

Cooper, Donald R., and Pamela S. Schindler. Business Research Methods. 8th ed. McGraw-Hill, 2003.