POLULYAKH, E. O. Kronrod–Reeb Graphs of Functions on Noncompact Two-Dimensional Surfaces. I. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 67, n. 3, p. 375–396, 2015. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1990. Acesso em: 5 dec. 2025.