Kato, Tosio <br/><br/>
Perturbation theory for linear operators / 

 - 2nd 
 - New York:  Springer-Verlag,  1976 
 - xxi, 619p. Bibl. Index. 
<br/><br/><label>ISBN: </label>9780387075587 
<br/><br/><label>Dewey Class. No.: </label>515.72  / K19.PT