Nurgabyl, D.N., and U.A. Bekish. “Asymptotic Expansion of the Solution of a Singularly Perturbed Boundary Value Problem With Boundary Initial Jumps”. Bulletin of the Karaganda University. Mathematics Series 88, no. 4 (December 29, 2017): 47–55. Accessed September 7, 2025. http://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/178.