UMEA UNIVERSITY MEDICAL DISSERTATIONS N. s. nr 76 538,940 BLOMQUIST HANS K. son Mental retardation in children . An epide-­ miological and etiological study of mentally retarded children born 1959—1970 in a northern Swedish county. Umea 1982 Larsson and Co: S Tryckeri 8 s . 145, il .+ wkŁ. s nlb . 2 Umea University Medical Dissertations N.s. n r 76