ELIASSON, Halldór I. On Variations of Metrics. Mathematica Scandinavica, Berkeley, CA, United States, v. 29, p. 317–327, 1971. DOI: 10.7146/math.scand.a-11058. Disponível em: https://journals.msp.org/mscand/article/view/2297. Acesso em: 25 jul. 2026.