APA (7th ed.) Citation

Geological Society of America & Graf, W. L. (1987). Geomorphic systems of North America. Geological Society of America.

Chicago Style (17th ed.) Citation

Geological Society of America and William L. Graf. Geomorphic Systems of North America. Boulder, Colo.: Geological Society of America, 1987.

MLA (9th ed.) Citation

Geological Society of America and William L. Graf. Geomorphic Systems of North America. Geological Society of America, 1987.