Wang , YiyingZou , Yongkui and Chai , Shimin. (2020). $(1+s)$-Order Convergence Analysis  of Weak Galerkin Finite Element Methods for Second Order Elliptic Equations.
            <i>Advances in Applied Mathematics and Mechanics</i>. <i>13</i> (3).
            554-568.
         doi:10.4208/aamm.OA-2020-0020