Cita APA (7th ed.)

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

Cita Chicago (17th ed.)

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

Cita MLA (9th ed.)

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