Mіtrоpоlskу Y. A. and Fоdchuk V. I., “Substantiation of the averaging method for differential-difference equations in the Hilbert space ”, Ukr. Mat. Zhurn., vol. 23, no. 6, pp. 745–752, Oct. 1971, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/8621