HANSEN, H. W. On the Gaussian Markoff spectrum. MATHEMATICA SCANDINAVICA, [S. l.], v. 43, p. 35–43, 1978. DOI: 10.7146/math.scand.a-11760. Disponível em: https://www.mscand.dk/article/view/11760. Acesso em: 5 may. 2024.