ELIASSON, H. I. On Variations of Metrics. MATHEMATICA SCANDINAVICA, [S. l.], v. 29, p. 317–327, 1971. DOI: 10.7146/math.scand.a-11058. Disponível em: https://www.mscand.dk/article/view/11058. Acesso em: 7 may. 2024.