Pireddu, Marina, and Fabio Zanolin. “Cutting Surfaces and Applications to Periodic Points and Chaotic-Like Dynamics”. Topological Methods in Nonlinear Analysis 30, no. 2 (December 1, 2007): 279–319. Accessed July 3, 2024. https://apcz.umk.pl/TMNA/article/view/TMNA.2007.030.