Sapagovas, Mifodijus, Kristina Pupalaigė, Regimantas Čiupaila, and Tadas Meškauskas. 2023. “On the Spectrum Structure for One Difference Eigenvalue Problem With Nonlocal Boundary Conditions”. Mathematical Modelling and Analysis 28 (3):522–541. https://doi.org/10.3846/mma.2023.17503.