V. V. Slyusarchuk, “Conditions for Instability of an Invariant Toroidal Manifold of a Discrete Dynamical System in a Banach Space”, Ukr. Mat. Zhurn., vol. 53, no. 4, pp. 572–576, Apr. 2001, Accessed: Apr. 13, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4280