APA (7th ed.) Citation

Roop, P., Roop, C., & Kells, V. A. (1992). One earth, a multitude of creatures. Walker.

Chicago Style (17th ed.) Citation

Roop, Peter, Connie Roop, and Valerie A. Kells. One Earth, a Multitude of Creatures. New York: Walker, 1992.

MLA (9th ed.) Citation

Roop, Peter, et al. One Earth, a Multitude of Creatures. Walker, 1992.