Kulik, V. L., and N. V. Stepanenko. “On Regularity of Certain Linear Expansions of Dynamical Systems on a Torus”. Ukrains’kyi Matematychnyi Zhurnal 54, no. 4 (April 25, 2002): 568-574. Accessed June 14, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4094.