APA
UNEP, World wide fund for nature & World Conservation Union. (1991). Caring for the earth: A strategy for sustainable living. London: Earthscan.
Chicago
UNEP, World wide fund for nature and World Conservation Union. 1991. Caring for the earth: A strategy for sustainable living. London: Earthscan.
Harvard
UNEP, World wide fund for nature and World Conservation Union. (1991). Caring for the earth: A strategy for sustainable living. London: Earthscan.
MLA
UNEP, World wide fund for nature and World Conservation Union. Caring for the earth: A strategy for sustainable living. London: Earthscan. 1991.