BoichukО. A. “Nonlinear Boundary-Value Problems for Systems of Ordinary Differential Equations”. Ukrains’kyi Matematychnyi Zhurnal 50, no. 2 (February 25, 1998): 162–171. Accessed September 1, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4951.