Heacox, K. (2016). National Geographic the national parks: An illustrated history. National Geographic.
Chicago-referens (17:e uppl.)Heacox, Kim. National Geographic the National Parks: An Illustrated History. Washington, D.C: National Geographic, 2016.
MLA-referens (9:e uppl.)Heacox, Kim. National Geographic the National Parks: An Illustrated History. National Geographic, 2016.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.