Tepoyan, L.P. “NONSELFADJOINT DEGENERATE DIFFERENTIAL EQUATIONS OF HIGHER ORDER”. Proceedings of the YSU A: Physical and Mathematical Sciences 48, no. 2 (234) (July 10, 2014): 24–29. Accessed July 22, 2024. https://journals.ysu.am/index.php/proceedings-phys-math/article/view/vol48_no2_2014_pp024-029.