Kudashov Z, Kaiyrbek OA. On biorthogonal property of systems of root functions of the Neumann problem for the perturbation of the integral boundary condition. JMMCS [Internet]. 2012 Jun. 28 [cited 2024 Dec. 22];73(2):31-8. Available from: https://bm.kaznu.kz/index.php/kaznu/article/view/134