Cita APA

National Geographic Society (Estados Unidos). National Geographic Maps, & Johns, C. (2007). A world transformed. Washington, D.C.: National Geographic.

Citación estilo Chicago

National Geographic Society (Estados Unidos). National Geographic Maps, y Chris Johns. A World Transformed. Washington, D.C.: National Geographic, 2007.

Cita MLA

National Geographic Society (Estados Unidos). National Geographic Maps, y Chris Johns. A World Transformed. Washington, D.C.: National Geographic, 2007.