National Geographic Society (U.S.). Book Division. (1997). Exploring America's historic places. The National Geographic Society.
Chicago-referens (17:e uppl.)National Geographic Society (U.S.). Book Division. Exploring America's Historic Places. Washington, D.C: The National Geographic Society, 1997.
MLA-referens (9:e uppl.)National Geographic Society (U.S.). Book Division. Exploring America's Historic Places. The National Geographic Society, 1997.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.