Messirdi, Sanaa, Mustapha Djaa, and Bekkai Messirdi. “Stability of Almost Closed Operators on a Hilbert Space”. Sarajevo Journal of Mathematics 5, no. 1 (June 11, 2024): 133–141. Accessed December 4, 2024. https://sjm.anubih.ba/index.php/sjm/article/view/358.