Não informado. (1973). Energy index. Environment Information Center, Energy Reference Department.
Chicago-referens (17:e uppl.)Não informado. Energy Index. New York: Environment Information Center, Energy Reference Department, 1973.
MLA-referens (8:e uppl.)Não informado. Energy Index. Environment Information Center, Energy Reference Department, 1973.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.