V. O. Livinskii, “Essential normality of some classes of operators in tensor products of Hilbert spaces”, Ukr. Mat. Zhurn., vol. 46, no. 7, pp. 878–885, Jul. 1994, Accessed: Feb. 17, 2026. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5679