“…Consequently, we have that div(P 1 (∇f )) = On the other hand, since M n+1 is an Einstein manifold with n ≥ 3, there exists a parameter λ ∈ R such that Ric = λ , , where Ric denotes the Ricci tensor of M n+1 . Thus, denoting by R the curvature tensor of M n+1 , from Lemma 25 of [5] (see also Lemma 3.1 of [2]) we have divP 1 , ∇f = i R(η, e i )∇f, e i = Ric(η, ∇f ) = λ η, ∇f = 0, where η stands for the unit normal vector field on M n . Hence, from (4.13), we conclude that (4.14) f = div(P 1 (∇f )).…”