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.
Citazione stile Chigago Style (17a edizione)International Union for Conservation of Nature and Natural Resources, United Nations Environment Programme, e 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.
Citatione MLA (9a ed.)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.