Feshchenko, S. F., Shkіl N. I., and Sоtnіchenkо N. A. “On Asymptotic Representation of Solutions for a System of Linear Partial Differential Equations With Time Lag”. Ukrains’kyi Matematychnyi Zhurnal 23, no. 2 (February 23, 1971): 177–189. Accessed December 6, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/8500.