1. Baer, D., Peterson, R., & Sherman, J. The development of imitation by reinforcing behavioral similarity to a model.Journal of the Experimental Analysis of Behavior, 1967,10, 405–416.
2. Bijou, S. A functional analysis of retarded development. In N. Ellis (Ed.),International review of research in mental retardation (Vol. 1). New York: Academic Press, 1966.
3. Brubeck, T., & Vanston, A. Designing day care centers.Mental Retardation, 1974,12, 32–33.
4. Council for Exceptional Children. The exceptional child's early years.Exceptional Children, 1971,39. (Special issue)
5. Dunn, L. M.Peabody Picture Vocabulary Test. Minneapolis, Minn.: American Guidance Service, 1959.