KUZMA, Bojan, 2008, Bendaoud, M.; Bourhim, A.; Sarih, M.: Linear maps preserving the essential spectral radius. (English). - [J] Linear Algebra Appl. 428, No. 4, 1041-1045 (2008). [ISSN 0024-3795]. [online]. 2008. [Accessed 24 April 2025]. Retrieved from: http://www.zentralblatt-math.org/zmath/en/advanced/?q=an:1135.47033