Ateiwi, A.M. (1997) “On the problem on periodic solutions of one class of systems of difference equations”, Ukrains’kyi Matematychnyi Zhurnal, 49(2), pp. 309–314. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/5008 (Accessed: 14 April 2025).