Não informado. (1956). Instructional materials. National Education Association, Department of Audio Visual Instruction.
Citação do estilo Chicago (17ª ed.)Não informado. Instructional Materials. Washington: National Education Association, Department of Audio Visual Instruction, 1956.
Citação MLA (8ª ed.)Não informado. Instructional Materials. National Education Association, Department of Audio Visual Instruction, 1956.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.