NICOLAU, A.; SUÁREZ, D. Approximation by invertible functions of $H^{\infty}$. MATHEMATICA SCANDINAVICA, [S. l.], v. 99, n. 2, p. 287–319, 2006. DOI: 10.7146/math.scand.a-15013. Disponível em: https://www.mscand.dk/article/view/15013. Acesso em: 5 may. 2024.