United Nations Environmental Program. (1987). State of the Environment: The state of the world environment. United Nations Environmental Program.
Chicago-viite (17. p.)United Nations Environmental Program. State of the Environment: The State of the World Environment. Nairobi, Kenya: United Nations Environmental Program, 1987.
MLA-viite (9. p.)United Nations Environmental Program. State of the Environment: The State of the World Environment. United Nations Environmental Program, 1987.
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