Marchuk, N. A., and Yu. V. Teplinsky. “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 December 6, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/3889.