Keskin, B., and S. A. Ozkan. “Spectral Problem for Discontinuous Integro-Differential Operator”. Ukrains’kyi Matematychnyi Zhurnal 64, no. 2 (February 25, 2012): 277-282. Accessed April 20, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/2575.