Helmberg, Gilbert. <br/><br/>
Introduction to spectral theory in hilbert space   
by Gilbert Helmberg 
 - Amsterdam  North-Holland  1967 
 - xiii, 346p. 
 - North-Holland Series in Applied Mathematics and Mechannics .
<br/><br/><label>LCCN: </label>68-16558 
<br/><br/><label>Dewey Class. No.: </label>515.73  / N69