Haldane, Robert A <br/><br/>
The hidden world 
R. A. Haldane 
 - London  R. Hale  1976 
 - 207 p. ; 23 cm 
<br/><br/> Includes bibliographical references and index 
<br/><br/><label>ISBN: </label>0709153511 
<br/><br/><label>ISSN: </label>76364726 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Cryptography - History
<br/><br/><label>Dewey Class. No.: </label>Z103 .H25 001.54/36