APA (7th ed.) Citation

United States. Office of National Capital Parks & United States. National Park Service. (2011). Washington, the nation's capital ([2011 revised edition].). National Capital Parks : National Park Service.

Chicago Style (17th ed.) Citation

United States. Office of National Capital Parks and United States. National Park Service. Washington, the Nation's Capital. [2011 revised edition]. [Washington, D.C.]: National Capital Parks : National Park Service, 2011.

MLA (9th ed.) Citation

United States. Office of National Capital Parks and United States. National Park Service. Washington, the Nation's Capital. [2011 revised edition]. National Capital Parks : National Park Service, 2011.