The wikipedia article includes references from a couple of decades earlier, at least; e.g. > Nat. Geographic: May 1974. "Tanna (Island, New Hebrides, South Pac

The wikipedia article includes references from a couple of decades earlier, at least; e.g. > Nat. Geographic: May 1974. "Tanna (Island, New Hebrides, South Pacific Ocean) Awaits the Coming of John Frum (cargo cults of Melanesia since about 1940)". (See https://georgehbalazs.com/wp-content/uploads/2019/08/TANNA-AWAITS-THE-COMING-OF-JOHN-FRUM-1974-National-Geographic.pdf https://georgehbalazs.com/wp-content/uploads/2019/08/TANNA-A... for a scan of the full article.)