1. Lebedev, VI: Evaluation of the error involved in the grid method for Newmann’s two dimensional problem. Sov. Math. Dokl. 1, 703-705 (1960)
2. Volkov, EA: On convergence in C 2 $C_{2}$ of a difference solution of the Laplace equation on a rectangle. Russ. J. Numer. Anal. Math. Model. 14(3), 291-298 (1999)
3. Dosiyev, AA, Sadeghi, HM: A fourth order accurate approximation of the first and pure second derivatives of the Laplace equation on a rectangle. Adv. Differ. Equ. 2015, 67 (2015). doi: 10.1186/s13662-015-0408-8
4. Volkov, EA: On the convergence in C h 1 $C_{h}^{1}$ of the difference solution to the Laplace equation in a rectangular parallelepiped. Comput. Math. Math. Phys. 45(9), 1531-1537 (2005)
5. Volkov, EA: On the grid method for approximating the derivatives of the solution of the Dirichlet problem for the Laplace equation on the rectangular parallelepiped. Russ. J. Numer. Anal. Math. Model. 19(3), 269-278 (2004)