1. Allen, G. (1958).Am J. Ment. Defic. 62:840.
2. Burt, C., and Howard, M. (1956). The multifactorial theory of inheritance and its application to intelligence.Brit. J. Stat. Psychol. 9:95?131.
3. Duncan, O. D., Featherman, D. L., and Duncan, B. (1968). Socioeconomic Background and Occupational Acheivement: Extensions of a Basic Model, Final Report Project No. 50074 (EO-191), U.S. Department of Health, Education and Welfare Office of Education, Bureau of Research, May.
4. Erlenmeyer-Kimling, L. and Jarvik, L. F. (1963). Genetics and intelligence: A review.Science 142:1477?1479.
5. Graves. W. L., Freeman, M. G. and Thompson, J. D. (1968). Culturally related reproductive factors in mental retardation. Paper read at Conference on Sociocultural Aspects of Mental Retardation Peabody College, Nashville, Tenn., June.