Burilko, O. A. “Separation of Variables in Linear Extensions of Dynamical Systems on Tori”. Ukrains’kyi Matematychnyi Zhurnal 48, no. 1 (January 25, 1996): 129–132. Accessed April 26, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/5371.