SHARKO, V. V. Smooth and Topological Equivalence of Functions on Surfaces. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 55, n. 5, p. 687–700, 2003. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3943. Acesso em: 5 dec. 2025.