Cita APA (7a ed.)
Allen, W. L. National Geographic: Vol. 199, no. 5, May 2001. National Geographic Society.
Cita estilo Chicago (17a ed.)
Allen, William L. National Geographic: Vol. 199, No. 5, May 2001. Washington, EUA: National Geographic Society.
Cita MLA (9a ed.)
Allen, William L. National Geographic: Vol. 199, No. 5, May 2001. National Geographic Society.
Precaución: Estas citas no son 100% exactas.