Bekkai MESSIRDI, Sanaa MESSIRDI, and Miloud MESSIRDI. “Drazin Invertibility of Sum and Product of Closed Linear Operators”. Malaya Journal of Matematik 2, no. 04 (October 1, 2014): 472–481. Accessed November 22, 2024. https://www.malayajournal.org/index.php/mjm/article/view/439.