IUCN yearbook, 1975-76 : annual report of the International Union for Conservation of Nature and Natural Resources for 1975 and for January-May 1976 1976
IUCN yearbook : annual report of the International Union for Conservation of Nature and Natural Resources for 1973 1974
IUCN yearbook : annual report of the International Union for Conservation of Nature and Natural Resources for 1972 1973
