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.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रInternational Union for Conservation of Nature and Natural Resources, World Wide Fund for Nature, और 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.
एमएलए (9वां संस्करण) प्रशस्ति पत्रInternational 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.