AmirovR. Kh., Güldü Y., and TopsakalN. 2010. “On Impulsive Sturm–Liouville Operators With Coulomb Potential and Spectral Parameter Linearly Contained in Boundary Conditions”. Ukrains’kyi Matematychnyi Zhurnal 62 (9), 1155–1172. https://umj.imath.kiev.ua/index.php/umj/article/view/2946.