International Union for Conservation of Nature and Natural Resources, United Nations Environment Programme, & World Wide Fund for Nature. (1991). Caring for the earth. IUCN--the World Conservation Union United Nations Environment Programme World Wide Fund for Nature.
Chicago-viite (17. p.)International Union for Conservation of Nature and Natural Resources, United Nations Environment Programme, ja World Wide Fund for Nature. Caring for the Earth. Gland, Switzerland: IUCN--the World Conservation Union United Nations Environment Programme World Wide Fund for Nature, 1991.
MLA-viite (9. p.)International Union for Conservation of Nature and Natural Resources, et al. Caring for the Earth. IUCN--the World Conservation Union United Nations Environment Programme World Wide Fund for Nature, 1991.