1.
図書 |
United States Department of the Interior, Bureau of Mines
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2.
図書 |
prepared by staff of the Bureau of Mines
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3.
図書 |
prepared by staff of the Bureau of Mines
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4.
図書 |
O.E. Kiessling, U.S. Department of Commerce, Bureau of Mines
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5.
雑誌 |
United States Department of the Interior, Geological Survey
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6.
図書 |
by E.A. Holbrook, Thomas Fraser
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