Não informado. (1967). Minerals Yearbook. U.S. Department of the Interior, Bureau of Mines.
Chicago-referens (17:e uppl.)Não informado. Minerals Yearbook. Washington: U.S. Department of the Interior, Bureau of Mines, 1967.
MLA-referens (8:e uppl.)Não informado. Minerals Yearbook. U.S. Department of the Interior, Bureau of Mines, 1967.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.