APA (7th ed.) Zitazioa
National Geographic Society. La tierra. National Geographic Society.
Chicago Style (17th ed.) Zitazioa
National Geographic Society. La Tierra. Buenos Aires: National Geographic Society.
MLA (9th ed.) Zitazioa
National Geographic Society. La Tierra. National Geographic Society.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.