Não informado. Topographic instructions of the United States Geological Survey. U.S. Department of the Interior.
Chicago-referens (17:e uppl.)Não informado. Topographic Instructions of the United States Geological Survey. Washington: U.S. Department of the Interior.
MLA-referens (8:e uppl.)Não informado. Topographic Instructions of the United States Geological Survey. U.S. Department of the Interior.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.