[1]
S. A. Kuzhel', “Spectral analysis of doubly $J$-nonexpanding operators”, Ukr. Mat. Zhurn., vol. 45, no. 3, pp. 384–388, Mar. 1993, Accessed: Feb. 17, 2026. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5820