Saaty, Thomas L. and Kainen, Paul C. <br/><br/>
The four-color problem; assaults and conquest   

 - 2nd. 
 - New York  Dover  1986 
 - vi, 217p. Index, Bibl. 
<br/><br/>  
<br/><br/><label>Dewey Class. No.: </label>511.5  / Sa112.FC