1. Allen, N. & Rushton, J. P. (1983). Personality characteristics of community health mental health volunteers: A review. Journal of Volunta y Action Research, 12,3649.
2. Alwin, D. F., Cohen, R. L. & Newcomb, T. M. (1991). Political attitudes over the life span. Madison: University of Wisconsin Press.
3. Astin, A. W. (1991). The American Freshman: National norms for Fall 1990. Washington, DC and Los Angeles: American Council on Education and University of California at Los Angeles.
4. Bachman, J. G. (1970). Youth in transition: Volume 11. The impact of family background and intelligence on tenth-grade boys. Ann Arbor, MI: Survey Research Center, Institute for Social Research.