APA (7th ed.) Citation

Humphrey, H. B. (1961). Makers of North American botany. Ronald Press.

Chicago Style (17th ed.) Citation

Humphrey, Harry B. Makers of North American Botany. New York: Ronald Press, 1961.

MLA (9th ed.) Citation

Humphrey, Harry B. Makers of North American Botany. Ronald Press, 1961.