Operation Trojan Horse (1970).
documentedbookFortean / Mothman / MIB
Keel's 1970 book arguing UFO reports are one continuum of weird events across history; the work that introduced/popularized the 'ultraterrestrial' framing.
Built directly on Vallée's Passport to Magonia (1969). Tied together monsters, ghosts, demons, the fairy faith, vampire legends, 1897 mystery airships, 1930s mystery aeroplanes, mystery helicopters, poltergeists, spheres of light, and UFOs as a single 'cover' phenomenon staged by non-human intelligence to propagate erroneous belief systems. Coined-popularized 'ultraterrestrials' (borrowed from N. Meade Layne).