Freeland, G. E. (1939). Learning activities with self-testing exercises for America and the new frontier. C. Scribner's Sons.
Lua i Stíl Chicago (17ú heag.)Freeland, George Earl. Learning Activities with Self-testing Exercises for America and the New Frontier. New York: C. Scribner's Sons, 1939.
Lua MLA (8ú heag.)Freeland, George Earl. Learning Activities with Self-testing Exercises for America and the New Frontier. C. Scribner's Sons, 1939.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.