“…Many numerical methods have been developed in the past a dozen years. Among existing works, four types of temporal discretization are most prevailing, i.e., finite difference methods (L-type schemes) [2,24,36,41], convolution quadrature methods [11,13,60,62], finite element methods [27,28,29,31] and spectral methods [26,35,55,64]. Under certain circumstances, problem (1) has an equivalent form like…”