SamoilenkoV. G. “Kato Inequality for Operators With Infinitely Many Separated Variables”. Ukrains’kyi Matematychnyi Zhurnal 51, no. 5 (May 25, 1999): 718–720. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4658.