 Robert Hahn and Scott Wallsten of the American Enterprise Institute wrote a paper in November 2003 directly criticising the Bessen/Hunt technique.Bessen and Hunt wrote a reply in 2004.A 2006 paper by Michael Noel and Mark Schankerman of the London School of Economics and Political Science also mentions the Bessen/Hunt technique and suggests that keyword searching can be difficult since many patent applications may contain the word software or other related words but not be primarily about software itself.