V. A. Kofanov, “The Bojanov – Naidenov problem for functions with nonsymmetric restrictions on the highest derivative”, Ukr. Mat. Zhurn., vol. 71, no. 3, pp. 368–381, Mar. 2019, Accessed: Apr. 23, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/1445