APA (7th ed.) Citation

Torrey, J., & Gray, A. (1969). A flora of North America. Hafner.

Chicago Style (17th ed.) Citation

Torrey, John, and Asa Gray. A Flora of North America. New York: Hafner, 1969.

MLA (9th ed.) Citation

Torrey, John, and Asa Gray. A Flora of North America. Hafner, 1969.