Ammar, Aymen, and S. Veeramani. “A Note on the Mapping Theorem of Essential Pseudospectra on a Banach Space”. Ukrains’kyi Matematychnyi Zhurnal 76, no. 3 (March 25, 2024): 341 - 352. Accessed May 10, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/7325.