Perturbation Theory for Linear Operators (Classics in Mathematics)

From the reviews: "[ ] An excellent textbook in the theory of linear operators in Banach and Hilbert spaces. It is a thoroughly worthwhile reference work both for graduate students in functional analysis as well as for researchers in perturbation, spectral, and scattering theory. [ ] I can recommend it for any mathematician or physicist interested in this field." Zentralblatt MATH