VRANCEANU, G. Variétés différentiables sans torsion. MATHEMATICA SCANDINAVICA, [S. l.], v. 21, p. 190–194, 1967. DOI: 10.7146/math.scand.a-10858. Disponível em: https://www.mscand.dk/article/view/10858. Acesso em: 4 may. 2024.