Kalimbetov, B. and Habibullaev, Z. (2015) “Regularization method for singularly perturbed integro-differential systems with multiple spectrum”, Bulletin of the Karaganda University. Mathematics Series, 80(4), pp. 91–97. Available at: https://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/66 (Accessed: 10 July 2025).