“…Since ξ α ω α = 0 = L ξ ω a , it follows that ω α is a vector also on S. Now, given g αβ , we can determine ξ α , and through that, λ, h ab and ω α , as well. Reversely, upon consideration of λ, ξ α , h ab , and ω α , it is possible to reconstruct the metric g αβ of M (see, e.g., [15]). Notice that, since ω α is a vector also on S, indices can be raised either by h ab or by g αβ .…”