Não informado. (1956). Bulletin. International Union for Conservation of Nature and Natural Resources.
Chicago-referens (17:e uppl.)Não informado. Bulletin. Brussels: International Union for Conservation of Nature and Natural Resources, 1956.
MLA-referens (8:e uppl.)Não informado. Bulletin. International Union for Conservation of Nature and Natural Resources, 1956.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.