BaranetskijYa. O., KalenyukP. I., and KolyasaL. I. “Spectral Properties of Nonself-Adjoint nonlocal boundary-Value Problems for the Operator of Differentiation of Even Order”. Ukrains’kyi Matematychnyi Zhurnal 70, no. 6 (June 25, 2018): 739-751. Accessed December 22, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/1592.