Lyndon, Roger C.   <br/><br/>
Combinatorial group theory   
by Roger C. Lyndon anf Paul E. Schupp 
 - New York  Springer  1977 
 - ix, 339 p. ; 23 cm. 
<br/><br/> Includes references and index 
<br/><br/><label>ISBN: </label>9783540411581   
<br/><br/><label>Dewey Class. No.: </label>512.22  / LYN