Não informado. (2021). Annual Bulletin of Gas Statistics for Europe and North America. United Nations.
Chicago-referens (17:e uppl.)Não informado. Annual Bulletin of Gas Statistics for Europe and North America. New York: United Nations, 2021.
MLA-referens (8:e uppl.)Não informado. Annual Bulletin of Gas Statistics for Europe and North America. United Nations, 2021.
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