Cita APA (7a ed.)
Graves, W. National Geographic: Vol. 180, no. 4, October 1991. National Geographic Society.
Cita estilo Chicago (17a ed.)
Graves, William. National Geographic: Vol. 180, No. 4, October 1991. Washington, EUA: National Geographic Society.
Cita MLA (9a ed.)
Graves, William. National Geographic: Vol. 180, No. 4, October 1991. National Geographic Society.
Precaución: Estas citas no son 100% exactas.