Mylyo, O. Y., & Storozh, O. G. (2002). A Differential Boundary Operator of the Sturm–Liouville Type on a Semiaxis with Two-Point Integral Boundary Conditions.
Ukrains’kyi Matematychnyi Zhurnal,
54(11), 1480-1485.
https://umj.imath.kiev.ua/index.php/umj/article/view/4186