“…Papers focusing on theoretical aspects include: the property of the price function such as differentiability, convexity, and put-call symmetry (Bergman, Grundy and Wiener (1996), McDonald andSchroder (1998), Shroder (1999)); the property of the critical stock price boundary (van Moerbeke (1976), Barles, Burdeau, Romano and Samsoen (1995), Peskir (2005), Zhu (2006); different formulations such as partial differential equation with free boundary (McKean (1965)), optimal stopping problem and its dual formulation (Bensoussan (1984), Karatzas (1988), Rogers (2002)), variational inequality (Jaillet, Lamberton and Lapeyre (1990)), and early exercise premium representation (Kim (1990), Jacka (1991), Carr, Jarrow and Myneni (1992)); 1 convergence and other properties of numerical methods (Lamberton (1993(Lamberton ( , 1998, Amin and Khanna (1994), Clément, Lamberton, and Protter (2002), Stentoft (2004)); and finally various generalizations such as general diffusion processes (Detemple and Tian (2002)), multiple underlying assets (Detemple, Feng and Tian (2003)), and more exotic American-type derivatives (see Detemple (2006)). …”