Ammar, Aymen, and S. Veeramani. “A Note on the Mapping Theorem of Essential Pseudospectra on a Banach Space”. Ukrains’kyi Matematychnyi Zhurnal, vol. 76, no. 3, Mar. 2024, pp. 341-52, https://doi.org/10.3842/umzh.v76i3.7325.