CLARKE A.D. /red./ Mental retardation and behavioural research otudy Group no.4. Study Group held at the University of Hull, under the auspices of the Institute for Research into Mental Retardation and with assistance from The Department of Education and Science. Ed. A.D. Clarke and A. M, Clarke, Edinburgh 1973 Churchill Livingstone 8° s,XII, 279. Institute for Research .into Mental Retardation.