Koshmanenko VD, Tuhai HV. On the structure of resolvent of singularly perturbed operator solving the problem of eigenvalues. Ukr. Mat. Zhurn. [Internet]. 2004Sep.25 [cited 2024May3];56(9):1292-7. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/3843