 However, Jerome Clark (Clark, 1993) notes that Jacques Vallée argued that the scientific content of the Ummo letters was knowledgeable but unremarkable, and compared the scientific references to a well-researched science fiction novel—plausible in the 1960s, but dated by the standards of the 1990s.Controversy arose about one particular assertion of the Ummites.In 1965, they wrote they were coming from a planet orbiting Wolf 424, adding this star is 3.68502 light-years of the Sun.