Não informado. (1967). Minerals Yearbook. U.S. Department of the Interior, Bureau of Mines.
Chicago-viite (17. p.)Não informado. Minerals Yearbook. Washington: U.S. Department of the Interior, Bureau of Mines, 1967.
MLA-viite (8. p.)Não informado. Minerals Yearbook. U.S. Department of the Interior, Bureau of Mines, 1967.
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