Gropper, G. L. (1974). Instructional strategies. Educational Technology.
Lua i Stíl Chicago (17ú heag.)Gropper, George L. Instructional Strategies. New Jersey: Educational Technology, 1974.
Lua MLA (9ú heag.)Gropper, George L. Instructional Strategies. Educational Technology, 1974.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.