Valiyev A, Valiyev M, Huseynov E. Spectrum and resolvent of multi-channel systems with internal energies and common boundary conditions. M [Internet]. 2024 Sep. 30 [cited 2025 Jul. 2];115(3):150-7. Available from: https://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/823