Valitskii YN, Golets BI, Zelenyak TI. Multipoint Boundary Conditions for Differential Operators. Ukr. Mat. Zhurn. [Internet]. 2003Jan.25 [cited 2024Jul.27];55(1):126-31. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/3894