Paukštaitė, Gailė, and Artūras Štikonas. “Nullity of the Second Order Discrete Problem With Nonlocal Multipoint Boundary Conditions”. Lietuvos matematikos rinkinys 56, no. A (December 23, 2015): 72–77. Accessed November 7, 2025. https://www.zurnalai.vu.lt/LMR/article/view/14935.