“…Versions of his formulation of the production process, which we will call "differential" in what follows, were used by many authors in several fields. Recent examples include Asea and Turnovsky (1998), Bianconi and Turnovsky (2005), Chatterjee, Giuliano and Turnovsky (2004), Chattopadhyay and Turnovsky (2003), Clemens and Soretz (2004), Corsetti (1997), Epaulart and Pommeret (2003), Evans and Kenc (2003), García-Peñalosa and , Gokan (2002), Gong andZou (2002, 2003), Grinols and Turnovsky (1993, 1994, 1998a, and 1998b), Kenc (2004), Pommeret and Smith (2005), Smith (1996), Steger (2005), Turnovsky (1993Turnovsky ( , 1999aTurnovsky ( , 1999b, and 2000), Turnovsky and Smith (2006) and Koethenbuerger and Lockwood (2009).…”