A convex polyhedron of $N_{\mathbb{R}}$ is a convex set defined as the intersection of a finite number of closed halfspaces. It is called strongly convex if it does not contain any line. A convex polyhedral cone is a convex polyhedron $\sigma$ such that $\lambda\sigma=\sigma$ for all $\lambda>0$. A polytope is a bounded convex polyhedron.