APA aipamena

Heffelfinger, C. H., & Weaver, R. B. (1939). Directed studies in world history. Mentzer, Bush & Co..

Chicago Style aipamena

Heffelfinger, C. H., and Robert B. Weaver. Directed Studies in World History. New York ; Chicago: Mentzer, Bush & Co., 1939.

MLA aipamena

Heffelfinger, C. H., and Robert B. Weaver. Directed Studies in World History. Mentzer, Bush & Co., 1939.