Klein, P. S. (1981)
Nutritional deprivation and retardation of cognitive functions. In P. Mittler (Ed.) Frontiers of Knowledge in Mental Retardation (vol. II). Baltimore : University Park Press
Chasey, W.C., Haywood, H.C., & Tzuriel,D. (1977).
Effects of various stimuli of activity level and learning by highand low-active retarded children. The Research Quarterly, 48, 265-269.