“…There is a large body of literature studying duopolistic advertising competition. Most of these papers (e.g., Bass et al 2005, Deal 1979, Erickson 1985, 1995, 2009, Fruchter 1999, Fruchter and Kalish 1997, Mesak and Calloway 1995, Naik et al 2008, Prasad and Sethi 2004, Sorger 1989, Wang and Wu 2001 investigate the advertising decisions of duopolistic firms without taking into consideration other marketing-mix variables. But there are certainly some exceptions, especially in the context of sponsored search advertising, where price competition has been considered together with advertising competition.…”