Dauylbayev, M. K., and A. B. Uaissov. 2019. “Asymptotic Behavior of the Solutions of Boundary-value problems for Singularly Perturbed Integro-Differential Equations”. Ukrains’kyi Matematychnyi Zhurnal 71 (11), 1466-79. https://umj.imath.kiev.ua/index.php/umj/article/view/1529.