MAKSIMENKO, S. I. Deformations of circle-valued Morse functions on surfaces. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 62, n. 10, p. 1360–1366, 2010. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2960. Acesso em: 5 dec. 2025.