Guy, Richard K. <br/><br/>
Unsolved Problems in Number Theory: Unsolved Problems Intuitive Mathematics vol. 

 - Berlin  Springer - Verlag Pub. .  1981 
 - xviii, 161 
<br/><br/><label>ISBN: </label>387905936 
<br/><br/><label>Dewey Class. No.: </label>510.'76