Não informado. (1964). Commodity Data Summaries. U.S. Department of the Interior, Bureau of Mines.
Chicago-Zitierstil (17. Ausg.)Não informado. Commodity Data Summaries. Washington: U.S. Department of the Interior, Bureau of Mines, 1964.
MLA-Zitierstil (8. Ausg.)Não informado. Commodity Data Summaries. U.S. Department of the Interior, Bureau of Mines, 1964.
Achtung: Diese Zitate sind unter Umständen nicht zu 100% korrekt.