Gropper, G. L., & Glasgow, Z. (1971). Criteria for the selection and use of visuals in instruction: A handbook. Educational Technology.
Lua i Stíl Chicago (17ú heag.)Gropper, George L., agus Zita Glasgow. Criteria for the Selection and Use of Visuals in Instruction: A Handbook. Englewood Cliffs, NJ: Educational Technology, 1971.
Lua MLA (9ú heag.)Gropper, George L., agus Zita Glasgow. Criteria for the Selection and Use of Visuals in Instruction: A Handbook. Educational Technology, 1971.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.