Dildabek, G., and A.A. Tengayeva. 2016. “Existence of Eigenvalues of Problem With Shift for an Equation of Parabolic-Hyperbolic Type”. Bulletin of the Karaganda University. Mathematics Series 82 (2):48-55. http://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/98.