Hansen, Vagn Lundsgaard, <br/><br/>
Braids and coverings :  selected topics / 
Vagn Lundsgaard Hansen. 
 - 191 páginas. 
 - London Mathematical Society Student Texts ;  no. 18 .
<br/><br/><label>ISBN: </label>0521387574 
<br/><br/><label>Dewey Class. No.: </label>515.16