INNAMI, N.; KIM, B. H. Gradient vector fields which characterize warped products. MATHEMATICA SCANDINAVICA, [S. l.], v. 88, n. 2, p. 182–192, 2001. DOI: 10.7146/math.scand.a-14322. Disponível em: https://www.mscand.dk/article/view/14322. Acesso em: 3 may. 2024.