[1]
G. V. Radzievskii, “On an upper bound for the number of characteristic values of an operator function”, Ukr. Mat. Zhurn., vol. 50, no. 2, pp. 211–224, Feb. 1998, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4956