GarrettH. E.Statistics in psychology and education.New York: Longmans, Green, 1954.
2.
HammillD. D., and IrwinO. C.An abstraction test adapted for use with mentally retarded children.American Journal of Mental Deficiency, 1966, 70, 807–812.
3.
IrwinO. C., and HammillD. D.An abstraction text for use with cerebral palsied children.Cerebral Palsy Review, 1964, 25, 3–9.