Cita APA (7a ed.)

Cunningham, W. P., & Cunningham, M. A. Principles of Environmental Science (9th ed.). Unknown.

Cita Chicago Style (17a ed.)

Cunningham, William P., y Mary Ann Cunningham. Principles of Environmental Science. 9th ed. Unknown: Unknown.

Cita MLA (9a ed.)

Cunningham, William P., y Mary Ann Cunningham. Principles of Environmental Science. 9th ed. Unknown.