1. Changes in IQ of a group of institutionalized mental defectives over a period of two decades;Alper;Amer. J. ment. Defic,1959
2. Effects of institutionalization on retarded children: A longitudinal cross institutional investigation;Balla;Amer. J. ment. Defic.,1974
3. The effect of age on the intellectual performance of mental defectives;Bell;J. Gerontology.,1960
4. Ability and accomplishment of persons earlier judged mentally deficient;Charles;Genet. Psychol. Monographs,1953
5. Cognitive and social changes in the feeble-minded three further studies;Clarke;Brit. J. Psychol.,1958