 Its author, Luke Tierney, wrote a 1990 book on it.XLispStat dates to the late 1980s/early 1990s and probably saw its greatest popularity in the early-to-mid 1990s with greatly declining usage since.In the 1990s it was in very widespread use in statistical education, but has since been mostly replaced by R. There is a paper explaining why UCLA's Department of Statistics abandoned it in 1998, and their reasons for doing so likely hold true for many other of its former users.