APA

Worcester P. G., . (1939). A textbook of geomorphology. New York: D.van Nostrand Company.

Chicago

Worcester Philip G, . 1939. A textbook of geomorphology. New York: D.van Nostrand Company.

Harvard

Worcester P. G., . (1939). A textbook of geomorphology. New York: D.van Nostrand Company.

MLA

Worcester Philip G, . A textbook of geomorphology. New York: D.van Nostrand Company. 1939.