1. Abramovitz HK, Richardson SA (1975) Epidemiology of severe mental retardation in children: Community studies. Am J Ment Def 80: 18–39
2. Ainsworth MDS (1974) The development of infant-mother attachment. In: Caldwell BM, Ricciuti HN (eds) Review of child development research, vol 3. University of Chicago Press, Chicago
3. Akert K (1979) Probleme der Hirnreifung. In: Lempp R (Hrsg) Teilleistungsstörungen im Kindesalter. Huber, Bern
4. Akesson HO (1961) Epidemiology and genetics of mental deficiency in a Southern Swedish population. Almquist & Wiksell, Uppsala
5. Akesson HO (1968) Severe mental deficiency in Sweden. A demographic, clinical, and genetic analysis. Elanders Boktryckerie, Göteborg