D. K. Khusanov, “On the Unique Solvability of a Nonautonomous Functional Differential Equation of Neutral Type”, Ukr. Mat. Zhurn., vol. 53, no. 8, pp. 1147–1152, Aug. 2001, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4332