WojtowiczB., and KulikV. L. “Linear Extensions of Dynamical Systems on a Torus That Possess Green-Samoilenko Functions”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 50, no. 2, Feb. 1998, pp. 178–188, https://umj.imath.kiev.ua/index.php/umj/article/view/4953.