Ammar, A., F. Z. Boutaf, and A. Jeribi. “Essential Spectra in Non-Archimedean Fields”. Matematychni Studii 58, no. 1 (October 31, 2022): 82-93. Accessed May 4, 2024. http://www.matstud.org.ua/ojs/index.php/matstud/article/view/293.