Duncan, D. (2009). The national parks: America's best idea : an illustrated history. New York: Alfred A. Knopf.
Trích dẫn kiểu ChicagoDuncan, Dayton. The National Parks: America's Best Idea : An Illustrated History. New York: Alfred A. Knopf, 2009.
Deismireacht MLADuncan, Dayton. The National Parks: America's Best Idea : An Illustrated History. New York: Alfred A. Knopf, 2009.
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