Kofanov, V. A. “The Bojanov – Naidenov Problem for Functions With Nonsymmetric restrictions on the Highest Derivative”. Ukrains’kyi Matematychnyi Zhurnal 71, no. 3 (March 25, 2019): 368-381. Accessed March 28, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/1445.