Nodal $\mathcal{O}(h^4)$-Superconvergence in 3D by Averaging Piecewise Linear, Bilinear, and Trilinear FE Approximations. JCM [Internet]. 2018 Aug. 22 [cited 2025 Dec. 5];28(1):1-10. Available from: https://www.global-sci.com/index.php/JCM/article/view/11969