Karpenko, O. V., V. I. Kravets, and A. N. Stanzhitskii. “Oscillation of Solutions of the Second-Order Linear Functional-Difference Equations”. Ukrains’kyi Matematychnyi Zhurnal 65, no. 2 (February 25, 2013): 226-235. Accessed January 28, 2023. https://umj.imath.kiev.ua/index.php/umj/article/view/2414.