United Nations Environmental Program. (1987). State of the Environment: The state of the world environment. United Nations Environmental Program.
Chicago-referens (17:e uppl.)United Nations Environmental Program. State of the Environment: The State of the World Environment. Nairobi, Kenya: United Nations Environmental Program, 1987.
MLA-referens (9:e uppl.)United Nations Environmental Program. State of the Environment: The State of the World Environment. United Nations Environmental Program, 1987.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.