United Nations Environmental Program. (1987). State of the Environment: The state of the world environment. United Nations Environmental Program.
芝加哥风格引文United Nations Environmental Program. State of the Environment: The State of the World Environment. Nairobi, Kenya: United Nations Environmental Program, 1987.
MLA引文United Nations Environmental Program. State of the Environment: The State of the World Environment. United Nations Environmental Program, 1987.
警告：这些引文格式不一定是100％准确.