Wilson, R <br/><br/>
Four colors suffice  how the map problem was solved 
R. Wilson 
 - Princeton  Princeton University Press  2014 
 - xii  199 
 - Princeton science library .
<br/><br/><label>ISBN: </label>9780691158228 
<br/><br/><label>Dewey Class. No.: </label>511.6  / WIL