RomanyshynI. M., and Synyts’kyiL. A. 1997. “Construction of Approximations for a Stationary Solution of a System of Singular Ordinary Differential Equations”. Ukrains’kyi Matematychnyi Zhurnal 49 (6), 774–778. https://umj.imath.kiev.ua/index.php/umj/article/view/5061.