APA (7th ed.) Citation

Atwater, R., Atwater, F., & Lawson, R. (1998). Mr. Popper's penguins. Scholastic.

Chicago Style (17th ed.) Citation

Atwater, Richard, Florence Atwater, and Robert Lawson. Mr. Popper's Penguins. New York: Scholastic, 1998.

MLA (9th ed.) Citation

Atwater, Richard, et al. Mr. Popper's Penguins. Scholastic, 1998.