Friedrichs, K. O <br/><br/>
Spectral theory of operators in Hilbert space 
K. O. Friedrichs 
 - New York  Springer-Verlag  1973 
 - VIII, 242 p  20 cm 
<br/><br/> Contine bibliogr. si index 
<br/><br/><label>ISBN: </label>3540900764