Não informado. (2021). Annual Bulletin of Coal Statistics for Europe and North America. United Nations.
Chicagoスタイル(17版)引用形式Não informado. Annual Bulletin of Coal Statistics for Europe and North America. New York: United Nations, 2021.
MLA(8版)引用形式Não informado. Annual Bulletin of Coal Statistics for Europe and North America. United Nations, 2021.
警告: この引用は必ずしも正確ではありません.