Singleton, R.A., Jr., & Straits, B.C. (2005) . Approaches to social research (4th Edition) New York: Oxford University Press.
Saunders, M., Lewis, P. & Thornhill, A (2009). Research methods for business students (5th ed.). Essex: Pearson Education Limited.
Nunnally, J. C., & Bernstein, I. H. (1994). Psychometrics theory (3rd ed.). New York: McGraw-Hill.
Mitchell, M. L., & Jolley, J. M. (2004). Research design explained (5th ed.). Toronto, Canada: Wadsworth.
Meltzoff, J. (1998). Critical thinking about research. Washington, D C: American Psychological Association.
DeVellis, R.F. (1991). Scale development: Theory and applications. London: Sage.
Christensen, L. B. (1997). Experimental methodology (7th ed.). Boston: Allyn & Bacon.
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