Štikonas, Artūras, and Olga Štikonienė. “Characteristic Functions for sturm—liouville Problems With Nonlocal Boundary Conditions”. Mathematical Modelling and Analysis 14, no. 2 (June 30, 2009): 229-246. Accessed November 12, 2024. https://transport.vilniustech.lt/index.php/MMA/article/view/6543.