Konstantinov, A. Yu. “Spectral and Scattering Theory of Some Matrix Operators Related to the Schrödinger Equations With Potentials Depending Rationally on Spectral Parameter”. Methods of Functional Analysis and Topology 2, no. 3 (December 25, 1996): 69–77. Accessed December 19, 2025. https://zen.imath.kiev.ua/index.php/mfat/article/view/21.