1. The President's committee on mental retardation, 1972 report. MR. 72: Islands of excellence, Washington, DC: Department of Health, Education and Welfare, p. 54.
2. The myth of 3% prevalence;Mercer,1973
3. Exceptionalities through the lifespan: An introduction;Cleland,1982
4. Office of Education, 1975 estimates, annual report.,1975