Kuznietsova, Iryna, and Sergiy Maksymenko. “Deformational Symmetries of Smooth Functions on Non-Orientable Surfaces”. Topological Methods in Nonlinear Analysis 65, no. 1 (February 13, 2025): 35–77. Accessed June 28, 2025. https://apcz.umk.pl/TMNA/article/view/58805.