APA(7版)引用形式

Não informado. (1931). International coal trade. U.S. Department of the Interior, Bureau of Mines.

Chicagoスタイル(17版)引用形式

Não informado. International Coal Trade. Washington: U.S. Department of the Interior, Bureau of Mines, 1931.

MLA(8版)引用形式

Não informado. International Coal Trade. U.S. Department of the Interior, Bureau of Mines, 1931.

警告: この引用は必ずしも正確ではありません.