Não informado. Topographic instructions of the United States Geological Survey. U.S. Department of the Interior.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Topographic Instructions of the United States Geological Survey. Washington: U.S. Department of the Interior.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Topographic Instructions of the United States Geological Survey. U.S. Department of the Interior.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.