Dymarskii, Ya. M. “Manifolds of Eigenfunctions and Potentials of a Family of Periodic Sturm–Liouville Problems”. Ukrains’kyi Matematychnyi Zhurnal 54, no. 8 (August 25, 2002): 1042-1052. Accessed May 9, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4145.