“…First, the principle of the so-called "cell-centered" schemes is to associate discrete unknowns with the cells of the mesh and to integrate the Laplace equation on each cell. Among various approaches, (which have been developed mainly for anisotropic diffusion, but which may of course be applied to the Laplace equation), we may cite [1,2,6,9,15,25,[29][30][31]. The principle of the second family, the so-called "vertex-centered" schemes, is to associate discrete unknowns with the vertices of the primal mesh, and then integrate the Laplace equation on the cells of a dual mesh, centered on the vertices [4,5,10,11,24,35].…”