Imanbaev, Nurlan, and Makhmud Sadybekov. “On Spectral Properties of a Periodic Problem With an Integral Perturbation of the Boundary Condition”. Eurasian Mathematical Journal 4, no. 3 (September 30, 2013): 53–62. Accessed September 30, 2025. https://emj.enu.kz/index.php/main/article/view/536.