1. Mental retardation: Definition, classification and systems of support;American Association on Mental Retardation,2002
2. Diagnostic and Statistical Manual of the Mental Disorders;American Psychiatric Association,1994
3. The self-perception of pupils with Down syndrome in relation to their academic competence, physical competence and social acceptance;Begley;International Journal of Disability, Development and Education,1999
4. An emerging European model for educational inclusion of troubled children;Bergsson;International Education,2003
5. Burley, S. K. (1995). Factors influencing the development of social competence in deaf and hard-of-hearing adolescents: An ecological approach. Dissertation, Faculty of The Graduate College at the University of Nebraska.