Teplins’kyi, O. Yu., and Yu. V. Teplinsky. 1996. “On the Erugin and Floquet-Lyapunov Theorems for Countable Systems of Difference Equations”. Ukrains’kyi Matematychnyi Zhurnal 48 (2), 278-84. https://umj.imath.kiev.ua/index.php/umj/article/view/5354.