“Browder Essential Approximate Pseudospectrum and Defect Pseudospectrum on a Banach Space: Doi:10.17398 2605-5686.34.1.29”. Extracta Mathematicae 34, no. 1 (June 1, 2019): 29–40. Accessed December 22, 2024. https://revista-em.unex.es/index.php/EM/article/view/2605-5686.34.1.29.