The World Book Encyclopedia 21 

 - Chicago :   World Book,   c2009 
 - 610 p.  : ill 
<br/><br/>Includes Bibliographical References and Index 
<br/><br/>v. 21. W-X-Y-Z  
<br/><br/><label>ISBN: </label>9780716601098 
<br/><br/><label>ISSN: </label>
<br/><br/><label>Subjects--Topical Terms: </label><br/>Encyclopedias and Dictionaries
<br/><br/><label>Dewey Class. No.: </label>031  / WOR