Friedrichs, K.O <br/><br/>
Spectral theory of operators in Hilbert space 
K.O. Friedrichs 
 - New York  Springer  1973 
 - viii  244 
 - Applied mathematical sciences 9 .
<br/><br/><label>ISBN: </label>3540900764 
<br/><br/><label>Dewey Class. No.: </label>5.03  / FRIE