International Union for Conservation of Nature and Natural Resources, World Wide Fund for Nature, & United Nations Environment Programme. (1991). Caring for the earth. IUCN-the World Conservation Union ; United Nations Environment Programme : World Wide Fund for Nature.
Style de citation Chicago (17e éd.)International Union for Conservation of Nature and Natural Resources, World Wide Fund for Nature, et United Nations Environment Programme. Caring for the Earth. Gland, Switzerland: IUCN-the World Conservation Union ; United Nations Environment Programme : World Wide Fund for Nature, 1991.
Style de citation MLA (9e éd.)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.