|   [1] Alvarez T. Perturbation and coperturbation functions characterising semi-Fredholm type operators. Mathematical Proceeding of the Royal Irish Academy, 1998, 98A(1): 41–46 
 
[2] Aiena P. Semi-fredholm operators, perturbation theory and localized svep. 2007 
 
[3] Caradus S R. Operators with finite ascent and descent. Pacific J Math, 1966, 18: 437–449 
 
[4] Fakhfakh F, Mnif M. Browder and Semi-Browder Operators and Perturbation Function. J Extracta Mathematicae, 2009, 24(3): 219–241 
 
[5] Fakhfakh F, Mnif M. Perturbation of semi-Browder operators and stability of Browder's essential defect and approximate point spectrum. J Math Anal Appl, 2008, 347: 235–242 
 
[6] Kaashoek M A. Ascent, descent, nullity and defect, a note on a paper by A. E. Taylor. Math Ann, 1967, 172: 105–115 
 
[7] Kaashoek M A, Lay D C. Ascent, descent and commuting perturbations. Trans Amer Math Soc, 1972, 169: 35–47 
 
[8] David Lay. Characterizations of the essential spectrum of F. E. Browder. Bul Amer Math Soc, 1968, 74: 246–248 
 
[9] Kato T. Perturbation theory for linear operators. Springer-Verlag, 1980 
 
[10] Marti J T. Operational calculus for two commuting closed operators. Comment Math Helv, 1968, 43: 87–97 
 
[11] M¨uller V. Spectral theory of linear operators and spectral system in Banach algebras. Operator theory advance and application vol. 139. 2003 
 
[12] Mbekhta M, Ouahab A. Op´erateur s-r´egulier dans un espace de Banach et th´eorie spectrale. Acta Sci Math, 1994, 59: 525–543 
 
[13] Rako?cevi´c V. Semi-Browder operators and perturbations. Studia Math, 1997, 122(2): 131–137 
 
[14] Rakoˇcevi´c V. Approximate point spectrum and commuting compact perturbation. Glasgow Math J, 1986, 28: 193–198 
 
[15] Reed M, Simon B. Methods of Modern Mathematical physics IV. Analysis of Operators. New York: Academic Press, 1978 
 
[16] Schechter M. Principles of Functional Analysis. Second Edition. American Mathematical Society, 2001  
 
[17] Taylor A E. Theorems on ascent, descent, nullity and defect of linear operators. Math Ann, 1966, 163: 18–49 
 
[18] West T T. A Riesz-Schauder theorem for semi-Fredholm operators. Proc Roy Irish Acad Sect, 1987, 87A: 137–146  |