Combinatorial group theory  
Lyndon, Roger C. 
 - Berlin ; | New York :  Springer,  2001 
 - xiv, 339 p. :  ill. ;  24 cm. 
 - Classics in mathematics, .
<br/><br/> Reprint of the 1977 edition." | "Originally published as Vol. 89 of the Ergibnisse der Mathematik und ihrer Grenzgebiete"--T.p. verso." 
<br/><br/><label>ISBN: </label>3540411585 (acid-free paper)