Kassymov, K A, M K Dauylbayev, and N Atakhan. 2012. “Symptotic Convergence of Solution of Boundary Problems for the Singular Perturbated Integro-Differential Equations”. Journal of Mathematics, Mechanics and Computer Science 74 (3):28-33. https://bm.kaznu.kz/index.php/kaznu/article/view/146.