1. Arbuckle, J. L. (1997). Amos user's guide (Version 3.6) [Computer software]. Chicago: SPSS.
2. Bentler, P. M. (1995). EQS structural equations program manual. Encino, CA: Multivariate Software.
3. Christofides, N. (1975). The theory and application of graphs. New York: Academic.
4. Gemignani, M. C. (1972). Elementary topology. Reading, MA: Addison-Wesley.
5. Joreskog, K. G. & Sorbom, D. (1996). LISREL 8: A guide to the program applications (2nd ed.). Chicago: Scientific Software International.