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.
Cita Chicago Style (17a ed.)National Parks Centennial Commission, United States. Servicio de Parques Nacionales, International Union for Conservation of Nature and Natural Resources, y World Conference on National Parks. Second World Conference on National Parks. Morges: International Union for Conservation of Nature and Natural Resources, 1974.
Cita MLA (8a ed.)National Parks Centennial Commission, et al. Second World Conference on National Parks. International Union for Conservation of Nature and Natural Resources, 1974.