KATO, Tosio Perturbation theory for linear operators /[by] Tosis Katto - 2nd ed. - Berlin Springer-Verlag 1984 - xxi, 619 p. Includes bibliography & index. ISBN: 3540075585 Subjects--Topical Terms: Linear operatorsPerturbation theory Dewey Class. No.: 515.7246 / KAT