Hartsfield, Nora. <br/><br/>
Pearls in graph theory :    a comprehensive introduction, 
Nora Hartsfield, Gerhard Ringel. 
 - Rev. and augm. 
 - Boston, Mass. :    Academic Press,    1994. 
 - 249 p. :   ill. ;    23 cm. 
<br/><br/>p. 241-244. 
<br/><br/><label>ISBN: </label>0123285534  RM105.07 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Graph theory.