Lucy <br/><br/>
George and the Unbreakable Code / 
Lucy and Stephen Hawking 
 - London:  Penguin,  c2014. 
 - 313 p. 
<br/><br/><label>ISBN: </label>9780552570053 
<br/><br/><label>Dewey Class. No.: </label>509.05   / LUC/G