Não informado. (2001). Annual report of the United States Geological Survey. U.S. Geological Survey.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Annual Report of the United States Geological Survey. Washington: U.S. Geological Survey, 2001.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Annual Report of the United States Geological Survey. U.S. Geological Survey, 2001.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.