Aisagaliev, S. A., M. N. Kalimoldayev, and E. M. Pozdeeva. “On the Boundary Problem of Ordinary Differential Equations”. Journal of Mathematics, Mechanics and Computer Science, vol. 75, no. 4, Dec. 2012, pp. 4-21, https://bm.kaznu.kz/index.php/kaznu/article/view/154.