Não informado. (1957). Annual Bulletin of Gas Statistics for Europe. United Nations, Economic Commission for Europe.
Chicago Style (17. basım) AtıfNão informado. Annual Bulletin of Gas Statistics for Europe. Geneva, Suíça: United Nations, Economic Commission for Europe, 1957.
MLA (8th ed.) AtıfNão informado. Annual Bulletin of Gas Statistics for Europe. United Nations, Economic Commission for Europe, 1957.
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