Wang , Bo and Wang , Li-Lian. (2014). On $L^2$-Stability Analysis of Time-Domain Acoustic Scattering Problems with Exact Nonreflecting Boundary Conditions.
            <i>Journal of Mathematical Study</i>. <i>47</i> (1).
            65-84.
         doi:10.4208/jms.v47n1.14.04