[1] K. Astala and H. O. Tylli, On the bounded compact approximation
property and measures of non-compactness, J. Funct. Anal. 70 (1987),
388-401.
[2] B. Aupetit, Propriétés Spectrales des Algèbres de Banach,
Lecture Notes in Mathematics 735 (1979).
[3] F. F. Bonsall and J. Duncan, Numerical ranges of operators on
normed spaces and of elements of normed algebras, London Math. Soc.
Lecture Note Series, 1971.
[4] F. F. Bonsall and J. Duncan, Complete Normed Algebras,
Springer-Verlag, 1973.
[5] R. Bouldin, The essential minimum modulus, Indiana Univ. Math. J.
30 (1981), 513-517.
[6] S. R. Caradus, W. E. Plaffenberger and B. Yood, Calkin Algebras
and Algebras of Operators on Banach Spaces, M. Dekker, New York,
1974.
[7] J. B. Conway, A Course in Functional Analysis, Second Edition,
Springer-Verlag, New York, 1990.
[8] R. G. Douglas, Banach Algebra Techniques in Operator Theory,
Academic Press, 1972.
[9] D. E. Edmunds and W. D. Evans, Spectral Theory and Differential
Operators, Clarendon Press, Oxford, 1987.
[10] F. Galaz-Fontes, Measures of non-compactness and upper
semi-Fredholm perturbation theorems, Proc. Amer. Math. Soc. 118
(1993), 891-897.
[11] F. Galaz-Fontes, Approximation by semi-Fredholm operators, Proc.
Amer. Math. Soc. 120 (1994), 1219-1222.
[12] H. A. Gindler and A. E. Taylor, The minimum modulus of a linear
operator and its use in spectral theory, Studia Math. 22 (1962/63),
15-41.
[13] S. Goldberg, Unbounded Linear Operators, McGraw-Hill, New York,
1966.
[14] M. Gonzalez and A. Martinon, Operational quantities
characterizing semi-Fredholm operators, Studia Math. 114 (1995),
13-27.
[15] P. Gopalraj and A. Ströh, On the essential lower bound of
elements in von Neumann algebras, Integral Equations Operator Theory
49 (2004), 379-386.
[16] R. Kadison and J. Ringrose, Fundamentals of the Theory of
Operator Algebras, Academic Press, Orlando, Vol. I, 1983.
[17] T. Kato, Perturbation theory for nullity, deficiency and other
quantities of linear operators, J. Analyse Math. 6 (1958), 261-322.
[18] A. Lebow and M. Schechter, Semigroups of operators and measures
of non-compactness, J. Funct. Anal. 7 (1971), 1-26.
[19] M. Mekhta, Fonctions perturbation et formules du rayon spectral
essentiel et de distance au spectrale essentiel, J. Operator Theory 51
(2004), 3-18.
[20] G. J. Murphy and T. T. West, Spectral radius formulae, Proc.
Edinburgh Math. Soc. (2) 22(3) (1979), 271-275.
[21] A. Pietsch, Operators Ideals, VEB Deutsch Verlag der
Wissenschaften, Berlin, 1978.
[22] C. E. Rickart, General Theory of Banach Algebras, Van Nostrand,
Princeton, 1960.
[23] M. Schechter, Quantities related to strictly singular operators,
Indiana Univ. Math. J. 21 (1972), 473-478.
[24] J. G. Stampfli and J. P. Williams, Growth conditions and the
numerical range in a Banach algebra, Tôhoku Math. J. 20 (1968),
417-424.
[25] H. O. Tylli, On the asymptotic behaviour of some quantities
related to semi-Fredholm operators, J. London Math. Soc. 31(2) (1985),
340-348.
[26] H. O. Tylli, The essential norm of an operator is not self-dual,
Israel J. Math. 91 (1995), 93-110.
[27] J. Zemánek, Geometric interpretations of the essential minimum
modulus, Invariant subspaces and other topics, Operator Theory: Adv.
Appl. Birkhäuser, Basel-Boston, Mass. 6 (1982), 225-227.
[28] J. Zemánek, The surjectivity radius, packing numbers and
boundedness below of linear operators, Int. Equa. Oper. Theory 6
(1983), 372-384.
[29] J. Zemánek, The semi-Fredholm radius of a linear operator,
Bull. Polish Acad. Sci. Math. 32 (1984), 67-76.
[30] J. Zemánek, Geometric characteristics of semi-Fredholm
operators and their asymptotic behaviour, Studia Math. 80 (1984),
219-234.
[31] S. Živković, Semi-Fredholm operators and perturbation
functions, Filomat 11 (1997), 77-88.
[32] S. Živković, Semi-Fredholm operators and perturbations,
Publ. Inst. Math. (Beograd) (N.S.) 61(75) (1997), 73-89.
[33] S. Živković, Measures of non-strict-singularity and
non-strict-cosingularity, Mat. Vesnik 54 (2002), 1-7.