Klecka, W. R., Nie, N., & Hull, C. H. SPSS primer: Statistical package for the social science primer. New York: McGraw-Hell Book Company.

Klecka, William R., Norman Nie, and C. Hadlai Hull. SPSS Primer: Statistical Package for the Social Science Primer. New York: McGraw-Hell Book Company.

Klecka, William R., Norman Nie, and C. Hadlai Hull. SPSS Primer: Statistical Package for the Social Science Primer. New York: McGraw-Hell Book Company.