GomilkoA. M., and PivovarchikV. N. “Inverse Sturm-Liouville Problem on a Figure-Eight Graph”. Ukrains’kyi Matematychnyi Zhurnal 60, no. 9 (September 25, 2008): 1168–1188. Accessed October 11, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3235.