Não informado. (1949). Annual Bulletin of Transport Statistics for Europe. United Nations, Economic Commission for Europe.
Chicago-referens (17:e uppl.)Não informado. Annual Bulletin of Transport Statistics for Europe. Geneve, Suíça: United Nations, Economic Commission for Europe, 1949.
MLA-referens (8:e uppl.)Não informado. Annual Bulletin of Transport Statistics for Europe. United Nations, Economic Commission for Europe, 1949.
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