Não informado. (1968). Annual Bulletin of General Energy Statistics for Europe. United Nations, Economic Commission for Europe.
Citação do estilo Chicago (17ª ed.)Não informado. Annual Bulletin of General Energy Statistics for Europe. New York: United Nations, Economic Commission for Europe, 1968.
Citação MLA (8ª ed.)Não informado. Annual Bulletin of General Energy Statistics for Europe. United Nations, Economic Commission for Europe, 1968.
警告：這些引文格式不一定是100％准確.