Pečiulytė, Sigita, and Artūras Štikonas. “On Positive Eigenfunctions of One Nonlocal Boundary Problem”. Lietuvos matematikos rinkinys 46, no. spec. (September 21, 2023): 313–317. Accessed November 7, 2025. https://www.zurnalai.vu.lt/LMR/article/view/15000.