Koshmanenko, V. D., and H. V. Tuhai. “Jacobi Matrices Associated With the Inverse Eigenvalue Problem in the Theory of Singular Perturbations of Self-Adjoint Operators”. Ukrains’kyi Matematychnyi Zhurnal 58, no. 12 (December 25, 2006): 1651–1662. Accessed April 20, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3561.