Perturbation Theory for Linear Operators (Classics in Mathematics, 132): Kato, Tosio: 9783540586616: Amazon.com: Books
Theory of Linear Operators in Hilbert Space,Linear Operators, Part 1: General Theory: Nelson Dunford, Jacob T. Schwartz: 9780471608486: Amazon.com: Books,Perturbation Theory for Linear Operators (Classics in Mathematics, 132): Kato, Tosio: 9783540586616: Amazon.com: Books,Perturbation Theory for Linear Operators (Classics in Mathematics, 132)