Não informado. (2011). U.S. Geological Survey Bulletin. U.S. Department of the Interior, Geological Survey.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. U.S. Geological Survey Bulletin. Washington: U.S. Department of the Interior, Geological Survey, 2011.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. U.S. Geological Survey Bulletin. U.S. Department of the Interior, Geological Survey, 2011.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.