Mirzakulova, A. E., and M. K. Dauylbayev. 2013. “Asymptotic Estimates of Solutions Boundary Value Problem for Singularly Perturbed Integro-Differential Equations”. Journal of Mathematics, Mechanics and Computer Science 76 (1):35-42. https://bm.kaznu.kz/index.php/kaznu/article/view/85.