MartynyukD. I., PerestyukN. A., and SamoilenkoA. M. “Reducibility of Nonlinear Almost Periodic Systems of Difference Equations Given on a Torus”. Ukrains’kyi Matematychnyi Zhurnal 46, no. 4 (April 25, 1994): 404–410. Accessed July 27, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5737.