John M. Clarke,  <br/><br/>
Education Department Bulletin No;492 December 1, 1911 

 - New York   University State  1911 
 - 65p. : ill , map :  21 cm 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Science 
<br/><br/><label>Universal Decimal Class. No.: </label>3a  / B6