P. A. Shvartsman, “Generalization of the Lidskii theorem on the localization of the spectrum of a product of Hermitian operators”, Ukr. Mat. Zhurn., vol. 51, no. 7, pp. 980–988, Jul. 1999, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4687