Gardner, Martin, <br/><br/>
Penrose tiles to trapdoor ciphers :  --and the return of Dr. Matrix / 
Martin Gardner. 
 - Rev. ed. 
 - Washington, D.C. :  Mathematical Association of America,  c1997. 
 - ix, 319 p. :  ill. (some col.) ; 
<br/><br/><label>ISBN: </label>0883855216 (pbk.) 
<br/><br/><label>Subjects--Index Terms: </label>Mathematical recreations 
<br/><br/><label>Universal Decimal Class. No.: </label>51-8  / GAR