National Parks Centennial Commission, United States. Servicio de Parques Nacionales, International Union for Conservation of Nature and Natural Resources, & World Conference on National Parks. (1974). Second world conference on national parks. International Union for Conservation of Nature and Natural Resources.
Style de citation Chicago (17e éd.)National Parks Centennial Commission, United States. Servicio de Parques Nacionales, International Union for Conservation of Nature and Natural Resources, et World Conference on National Parks. Second World Conference on National Parks. Morges: International Union for Conservation of Nature and Natural Resources, 1974.
Style de citation MLA (8e éd.)National Parks Centennial Commission, et al. Second World Conference on National Parks. International Union for Conservation of Nature and Natural Resources, 1974.