1. American Association on Intellectual and Developmental Disabilities (2010). http://www.aamr.org/content_100.cfm?navID=21. Accessed 16.02.10.
2. An epidemiological study of disability in 4-year-old children from a birth cohort in Frederiksborg County, Denmark;Andersen;Danish Medical Bulletin,1990
3. Prevalence, aetiology and comorbidity of severe and profound intellectual disability in Finland;Arvio;Journal of Intellectual Disability Research,2003
4. Mental retardation in over half-a-million consecutive livebirths: An epidemiological study;Baird;American Journal of Mental Deficiency,1985
5. Prevalence of intellectual disability in northern Sydney adults;Beange;Journal of Intellectual Disability Research,1996