LAWRYNOWICZ, J.; WALISZEWSKI, W. Conformality and Pseudo-Riemannian Manifolds. Mathematica Scandinavica, Berkeley, CA, United States, v. 28, p. 45–69, 1971. DOI: 10.7146/math.scand.a-11005. Disponível em: https://journals.msp.org/mscand/article/view/2292. Acesso em: 25 jul. 2026.