APA (7th ed.) Citation

National Geographic Society (U.S.). (2012). Guide to the national parks of the United States (7th edition.). National Geographic Publishers Group UK [distributor].

Chicago Style (17th ed.) Citation

National Geographic Society (U.S.). Guide to the National Parks of the United States. 7th edition. Washington, D.C., Enfield: National Geographic Publishers Group UK [distributor], 2012.

MLA (9th ed.) Citation

National Geographic Society (U.S.). Guide to the National Parks of the United States. 7th edition. National Geographic Publishers Group UK [distributor], 2012.