Não informado. (1999). United States Geological Survey Yearbook. U.S. Geological Survey.
Chicago-viite (17. p.)Não informado. United States Geological Survey Yearbook. Washington: U.S. Geological Survey, 1999.
MLA-viite (8. p.)Não informado. United States Geological Survey Yearbook. U.S. Geological Survey, 1999.
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