Zhengzhi Li,  Daniel Watson,  Ming Li &  Thir Dangal. (1970). The LMAPS Using Polynomial Basis Functions for Near-Singular Problems.
            <i>Advances in Applied Mathematics and Mechanics</i>. <i>10</i> (5).
            1090-1102.
         doi:10.4208/aamm.OA-2017-0288