Aslanova, N. M., and M. Bairamogly. “Distribution of Eigenvalues and Trace Formula for the Sturm–Liouville Operator Equation”. Ukrains’kyi Matematychnyi Zhurnal 62, no. 7 (July 25, 2010): 867–877. Accessed April 28, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/2920.