Cita APA (7th ed.)

Horkheimer, M., & Diffor, J. W. Educator's guide to free filmstrips. Educator's Progress Service.

Cita Chicago (17th ed.)

Horkheimer, Mary, i John Warren Diffor. Educator's Guide to Free Filmstrips. Randolph, Wisconsin: Educator's Progress Service.

Cita MLA (9th ed.)

Horkheimer, Mary, i John Warren Diffor. Educator's Guide to Free Filmstrips. Educator's Progress Service.