Feng , QiweiHan , Bin and Michelle , Michelle. (2023). Sixth-Order Compact Finite Difference Method for 2D Helmholtz Equations with Singular Sources and Reduced Pollution Effect.
            <i>Communications in Computational Physics</i>. <i>34</i> (3).
            672-712.
         doi:10.4208/cicp.OA-2023-0062