Theoretical models studying the labor mobility channel include Kaufmann (1997), Haaker (1999), Fosfuri, Motta, and Rønde (2001) and Glass and Saggi (2002). Rodriguez-Clare (1996) outlines forward and backward linkages between foreign firms and domestic firms as a possible mechanism for positive spillovers. Wang and Blomstrom (1992) emphasize the role of competition and also allude to the role of demonstration.