APA (7e ed.) Bronvermelding

Não informado. (1991). Research and Exploration. National Geographic Society.

Chicago (17e ed.) Bronvermelding

Não informado. Research and Exploration. Gaithersburg, Md: National Geographic Society, 1991.

MLA (8e ed.) Bronvermelding

Não informado. Research and Exploration. National Geographic Society, 1991.

Let op: Deze citaties zijn niet altijd 100% accuraat.