Freeland, G. E. (1939). Learning activities with self-testing exercises for America and the new frontier. C. Scribner's Sons.
Chicago-referens (17:e uppl.)Freeland, George Earl. Learning Activities with Self-testing Exercises for America and the New Frontier. New York: C. Scribner's Sons, 1939.
MLA-referens (8:e uppl.)Freeland, George Earl. Learning Activities with Self-testing Exercises for America and the New Frontier. C. Scribner's Sons, 1939.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.