Não informado. Statistical and other data on minerals: Quarterly information circular. Republic of South Africa, Department of Mines.
Chicago-referens (17:e uppl.)Não informado. Statistical and Other Data on Minerals: Quarterly Information Circular. Pretoria, Africa do Sul: Republic of South Africa, Department of Mines.
MLA-referens (8:e uppl.)Não informado. Statistical and Other Data on Minerals: Quarterly Information Circular. Republic of South Africa, Department of Mines.
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