MarchukN. A., and TeplinskyYu. V. “On the Fréchet Differentiability of Invariant Tori of Countable Systems of Difference Equations Defined on Infinite-Dimensional Tori”. Ukrains’kyi Matematychnyi Zhurnal 55, no. 1 (January 25, 2003): 75-90. Accessed July 27, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3889.