Superconvergence analysis of lower order anisotropic finite element

The convergence analysis of the lower order nonconforming element pro- posed by Park and Sheen is applied to the second-order elliptic problem under anisotropic meshes.The corresponding error estimation is obtained.Moreover,by using the interpo- lation postprocessing technique,a global superconvergence property for the discretization error of the postprocessed discrete solution to the solution itself is derived.Numerical results are also given to verify the theoretical analysis.