Não informado. (1973). Energy index. Environment Information Center, Energy Reference Department.
Chicago-viite (17. p.)Não informado. Energy Index. New York: Environment Information Center, Energy Reference Department, 1973.
MLA-viite (8. p.)Não informado. Energy Index. Environment Information Center, Energy Reference Department, 1973.
Varoitus: Nämä viitteet eivät aina ole täysin luotettavia.