“…The following material can be found in different forms and flavours in various sources, for instance in [15,18,19,25,26,[29][30][31]. We will in particular make use of [31] and [18,19]. Any manifold with corners has, locally, product coordinates ( , ) ∈ ℝ + × ℝ − = ℝ , where the vanishing of the determines the boundary hypersurfaces.…”