Hilbert space problem book  
Halmos, Paul R. 
 - 2nd ed., rev. and enl. ed. 
 - New York :  Springer-Verlag,  1982 
 - xvii, 369 p. ;  25 cm. 
 - Graduate texts in mathematics ;  19 .
<br/><br/> Includes index. 
<br/><br/><label>ISBN: </label>0387906851 :