Zubkova, E. I., and F. S. Rofe-Beketov. “Inverse Scattering Problem on the Axis for the Triangular $2\times 2$ Matrix Potential With a Virtual Level”. Methods of Functional Analysis and Topology 15, no. 4 (December 25, 2009): 301–321. Accessed December 16, 2025. https://zen.imath.kiev.ua/index.php/mfat/article/view/426.