Assanova, A.T., and A.E. Imanchiev. 2016. “On the Solvability of a Nonlocal Boundary Value Problem for a Loaded Hyperbolic Equations With Multi-Point Conditions”. Bulletin of the Karaganda University. Mathematics Series 81 (1):15-25. https://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/72.