Some optimality conditions of quasilinear elliptic obstacle optimal control problems. - Yuquan Ye; Chi Kin Chan; Bartholomew P. K. Leung (Appl. Math. Comput., 2007)

The existence results for obstacle optimal control problems. - Yuquan Ye; Chi Kin Chan; H. W. Joseph Lee (Appl. Math. Comput., 2009)