APA (7e ed.) Bronvermelding
Allen, W. L. National Geographic: Vol. 191, no. 1, January 1997. National Geographic Society.
Chicago (17e ed.) Bronvermelding
Allen, William L. National Geographic: Vol. 191, No. 1, January 1997. Washington, EUA: National Geographic Society.
MLA (9e ed.) Bronvermelding
Allen, William L. National Geographic: Vol. 191, No. 1, January 1997. National Geographic Society.
Let op: Deze citaties zijn niet altijd 100% accuraat.