Muratbekov, M.B., S.Zh. Igisinov, B.M. Musilimov, and R.R. Makulbekova. 2020. “On the Spectral Properties of a Class of High-Order Differential Operators With Operator Coefficients”. Bulletin of the Karaganda University. Mathematics Series 98 (2):110-24. https://doi.org/10.31489/2020m2/110-124.