Cita APA

Youth, H., & Prugh, T. (2003). Winged messengers: The decline of birds. Washington, D.C.: Worldwatch Institute.

Citación estilo Chicago

Youth, Howard, y Thomas Prugh. Winged Messengers: The Decline of Birds. Washington, D.C.: Worldwatch Institute, 2003.

Cita MLA

Youth, Howard, y Thomas Prugh. Winged Messengers: The Decline of Birds. Washington, D.C.: Worldwatch Institute, 2003.