Amirov, R. Kh., and V. A. Yurko. “On Differential Operators With Singularity and Conditions of Discontinuity Inside an Interval”.
Ukrains’kyi Matematychnyi Zhurnal, vol. 53, no. 11, Nov. 2001, pp. 1443-57,
https://umj.imath.kiev.ua/index.php/umj/article/view/4364.