1. Allison, P.B. (2001). Missing data. Thousand Oaks. CA: Sage.
2. Bartholomew, D. J. (1996). The statistical approach to social measurement. London: Academic Press.
3. Bentler, P. M. (2004). EQS structural equation program manual. Encino, CA: Multivariate Software.
4. Bollen, K. A. (1989). Structural equations with latent variables. New York: Wiley.
5. Crocker, L. & Algina, J. (1986). Introduction to classical and modern test theory. Fort Worth, TX: Har-court Brace Jovanovich.