P. G. Ermolaeva and V. B. Cherepennikov, “Polynomial quasisolutions of linear second-order differential-difference equations”, Ukr. Mat. Zhurn., vol. 60, no. 1, pp. 140–152, Jan. 2008, Accessed: Apr. 07, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3144