Não informado. (1956). Instructional materials. National Education Association, Department of Audio Visual Instruction.
Chicago-referens (17:e uppl.)Não informado. Instructional Materials. Washington: National Education Association, Department of Audio Visual Instruction, 1956.
MLA-referens (8:e uppl.)Não informado. Instructional Materials. National Education Association, Department of Audio Visual Instruction, 1956.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.