GrechkoA. L. “On Necessary Conditions for the Weak Regularity of a Linear Extension of a Dynamical System on a Torus”. Ukrains’kyi Matematychnyi Zhurnal 50, no. 3 (March 25, 1998): 424–425. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4942.