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2. Relative importance of genetic and non-genetic etiologies in idiopathic mental retardation: estimates based on analysis of medical histories;Costeff, H.; Cohen, B.E.; Weller, L.;Ann Hum Genet,1983
3. Clinical assessment of 4,500 developmentally delayed individuals;Einfeld, J.M.;J Ment Defic Res,1984
4. The socio-familial background and prevalence of medical aetiological factors in children attending ESN(M) schools;Lamont, M.A.;J Ment Defic Res,1988
5. WHO expert committee on mental health;World Health Organisation,1968