“…Unfortunately, the exact nonreflecting boundary conditions are generally nonlocal in both space and time, so that direct implementation is highly inefficient in terms of both computation and storage cost. Hence most research has been devoted to approximations of the exact nonreflecting boundary conditions, particularly for the one-dimensional case (see, e.g., [3,4,8,17,23,24,25,26]). A few papers in the literature consider the two-dimensional setting [5,7,22].…”