United Nations Educational Scientific and Cultural Organization. (1973). The Present situation and trends of research in the field of special education, four studies: Sweden and other Scandinavian countries, Union of Soviet Socialist Republics, United States of America, Uruguay. Unesco.

United Nations Educational Scientific and Cultural Organization. The Present Situation and Trends of Research in the Field of Special Education, Four Studies: Sweden and Other Scandinavian Countries, Union of Soviet Socialist Republics, United States of America, Uruguay. Paris: Unesco, 1973.

United Nations Educational Scientific and Cultural Organization. The Present Situation and Trends of Research in the Field of Special Education, Four Studies: Sweden and Other Scandinavian Countries, Union of Soviet Socialist Republics, United States of America, Uruguay. Unesco, 1973.