Pečiulytė, Sigita, and Artūras Štikonas. “Sturm–Liouville Problem With Two Point Nonlocal Second Type Boundary Condition”.
Lietuvos matematikos rinkinys 45, no. spec. (December 18, 2005): 432–436. Accessed April 16, 2025.
https://www.journals.vu.lt/LMR/article/view/14653.