Buterin, Sergey. “An Inverse Spectral Problem for Sturm-Liouville-Type Integro-Differential Operators With Robin Boundary Conditions”. Tamkang Journal of Mathematics 50, no. 3 (September 2, 2019): 207–221. Accessed April 29, 2024. https://journals.math.tku.edu.tw/index.php/TKJM/article/view/3347.