Arabyan, M. H. “ON AN EIGENVALUE PROBLEM”. Proceedings of the YSU A: Physical and Mathematical Sciences 39, no. 3 (208) (October 20, 2005): 31–39. Accessed November 23, 2024. https://journals.ysu.am/index.php/proceedings-phys-math/article/view/vol39_no3_2005_pp031-039.