Kato, T <br/><br/>
Perturbation theory for linear operators 
T. Kato 
 - 2 
 - Berlin  Springer  1995 
 - xvii  619 
 - Classics in mathematics .
<br/><br/><label>ISBN: </label>9783540586616 
<br/><br/><label>Dewey Class. No.: </label>5.03  / KATO