Encyclopoedia Britannica Put . Ltd. <br/><br/>
Britannica ready reference  encyclopedia .  vol  : 1 

 - New Delhi :  Encyclopaedia Britannica Pvt Ltd,  1994 
 - 268. 
<br/><br/><label>ISBN: </label>8181310985  
<br/><br/><label>Subjects--Topical Terms: </label><br/>Systems
<br/><br/><label>Dewey Class. No.: </label>003  / ENC