APA (7th ed.) Citation

Little, E. L. (1988). The Audubon Society field guide to North American trees: Western region (Sixth printing.). Knopf.

Chicago Style (17th ed.) Citation

Little, Elbert L. The Audubon Society Field Guide to North American Trees: Western Region. Sixth printing. New York: Knopf, 1988.

MLA (9th ed.) Citation

Little, Elbert L. The Audubon Society Field Guide to North American Trees: Western Region. Sixth printing. Knopf, 1988.