StanzhitskiiA. N., and TkachukA. M. “On the Relationship Between Properties of Solutions of Difference Equations and the Corresponding Differential Equations”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 57, no. 7, July 2005, pp. 989–996, https://umj.imath.kiev.ua/index.php/umj/article/view/3657.