ZernovA. E., and ChaichukO. R. “Qualitative Investigation of a Singular Cauchy Problem for a Functional Differential Equation”. Ukrains’kyi Matematychnyi Zhurnal 57, no. 10 (October 25, 2005): 1344–1358. Accessed July 27, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3690.