"VALIS" (1980) is perhaps Dick's most postmodern and autobiographical novel, examining his own unexplained experiences. It may also be his most academically studied work, and was adapted as an opera by Tod Machover. Later works like the VALIS trilogy were heavily autobiographical, many with "two-three-seventy-four" (2-3-74) references and influences. The word VALIS is the acronym for "Vast Active Living Intelligence System". Later, Dick theorized that VALIS was both a "reality generator" and a means of extraterrestrial communication. A fourth VALIS manuscript, "Radio Free Albemuth", although composed in 1976, was posthumously published in 1985. This work is described by the publisher (Arbor House) as "an introduction and key to his magnificent VALIS trilogy".