Maksimenko, S. I., & Feshchenko, B. G. (2014). Homotopic Properties of the Spaces of Smooth Functions on a 2-Torus. Ukrains’kyi Matematychnyi Zhurnal, 66(9), 1205–1212. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/2211