Martynyuk, D. I., Mitropolskiy, Y. A., & Tynnyi, V. I. (1993). Reducibility of linear systems of difference equations with almost periodic coefficients. Ukrains’kyi Matematychnyi Zhurnal, 45(12), 1661–1667. https://umj.imath.kiev.ua/index.php/umj/article/view/5974