Não informado. Visual education. National Committee for Visual Aids in Education.
Chicago-referens (17:e uppl.)Não informado. Visual Education. London: National Committee for Visual Aids in Education.
MLA-referens (8:e uppl.)Não informado. Visual Education. National Committee for Visual Aids in Education.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.