Sapagovas, Mifodijus, Regimantas Čiupaila, Kristina Jakubėlienė, and Stasys Rutkauskas. 2019. “A New Eigenvalue Problem for the Difference Operator With Nonlocal Conditions”. Nonlinear Analysis: Modelling and Control 24 (3): 462-84. https://doi.org/10.15388/NA.2019.3.9.