Muratbekov, M.B., and M.M. Muratbekov. “Smoothness and Approximative Properties of Solutions of the Singular Nonlinear Sturm-Liouville Equation”. Bulletin of the Karaganda University. Mathematics Series 100, no. 4 (December 30, 2020): 113–124. Accessed September 4, 2025. http://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/391.