Ivanov, I.A., A.N. Yesbayev, G.A. Yessenbayeva, and M.I. Ramazanov. 2015. “On the Solution of Boundary Value Problems by the Spectral Element Method”. Bulletin of the Karaganda University. Mathematics Series 79 (3):50-54. https://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/47.