Appel, Kenneth <br/><br/>
Every planar map is four colorable / 
Kenneth Appel, and Wolfgang Haken. 
 - 1a ed. 
 - Providence :  Rhode Island American Mathematical society,   1989 
 - xiv, 741 p. :  il. ;  26 cm. 
 - (Contemporary Mathematics ; )  V.98 .
<br/><br/><label>ISBN: </label>0821851039 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Problemas de los cuatro colores
<br/><br/><label>LC Class. No.: </label>QA612.18  / A67 1989