Gorodnii, M. F., and A. Ya. Dorogovtsev. “Bounded Solutions of One Class of Nonlinear Operator Difference Equations”. Ukrains’kyi Matematychnyi Zhurnal 47, no. 7 (July 25, 1995): 890–896. Accessed December 5, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/5483.