Browder essential approximate pseudospectrum and defect pseudospectrum on a Banach space: doi:10.17398/2605-5686.34.1.29. Extr. Math. [Internet]. 2019 Jun. 1 [cited 2024 Dec. 22];34(1):29-40. Available from: https://revista-em.unex.es/index.php/EM/article/view/2605-5686.34.1.29