Não informado. (2001). Annual report of the United States Geological Survey. U.S. Geological Survey.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रNão informado. Annual Report of the United States Geological Survey. Washington: U.S. Geological Survey, 2001.
एमएलए (8वां संस्करण) प्रशस्ति पत्रNão informado. Annual Report of the United States Geological Survey. U.S. Geological Survey, 2001.
चेतावनी: ये उद्धरण हमेशा 100% सटीक नहीं हो सकते हैं.