1. Bauer, Raymond A., ed. (1966), Social Indicators. Cambridge: M.I.T. Press.
2. Blau, Peter M., and Otis Dudley Duncan (1967), The American Occupational Structure. New York: Wiley.
3. Congressional Record (1967), Vol. 113, No. 17, February 6, 1967.
4. Ferriss, Abbott (1969), Indicators of Trends in American Education. New York: Russell Sage Foundation.
5. Goldhammer, Herbert, and A. W. Marshall (1953), Psychosis and Civilization: Studies in the Frequency of Mental Disease. Glencoe: Free Press.