Não informado. (1968). Annual Bulletin of Coal Statistics for Europe. United Nations, Economic Commission for Europe.
Chicagoスタイル(17版)引用形式Não informado. Annual Bulletin of Coal Statistics for Europe. New York: United Nations, Economic Commission for Europe, 1968.
MLA(8版)引用形式Não informado. Annual Bulletin of Coal Statistics for Europe. United Nations, Economic Commission for Europe, 1968.
警告: この引用は必ずしも正確ではありません.