[1]
L. P. Nizhnik and S. A. Kuzhel, “Finite rank self-adjoint perturbations”, MFAT, vol. 12, no. 3, pp. 243–253, Sep. 2006, Accessed: Feb. 04, 2026. [Online]. Available: https://zen.imath.kiev.ua/index.php/mfat/article/view/317