Harutyunyan, T. A. “THE PROBLEM OF OWN VALUES AND OWN FUNCTIONS IN THE TOROIDAL CAVITY”. Proceedings of the YSU A: Physical and Mathematical Sciences 39, no. 3 (208) (October 20, 2005): 64–72. Accessed July 22, 2024. https://journals.ysu.am/index.php/proceedings-phys-math/article/view/vol39_no3_2005_pp64-72.