MAKSYMENKO, S.; FESHCHENKO, B. Smooth functions on 2-torus whose Kronrod-Reeb graph contains a cycle. Methods of Functional Analysis and Topology, [S. l.], v. 21, n. 1, p. 22–40, 2015. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/598. Acesso em: 16 dec. 2025.