“…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]. More recently, a third family of schemes has emerged, which combines the previous two approaches, since these schemes associate unknowns with both the cells and the vertices of the mesh, and integrate the Laplace equation on both the cells of the primal and dual meshes [3,13,16,18,19,26,27,33]. The originality of these schemes is that they work well on all kind of meshes, including very distorted, degenerating, or highly nonconforming meshes (see the numerical tests in [19]).…”