Encylopaedia Britannica Pvt Ltd. <br/><br/>
Britannica learning library 

 - New Delhi :  Encyclopaedia Britannica Pvt Ltd,  1994 
 - 574. 
<br/><br/><label>ISBN: </label>1593392672  
<br/><br/><label>Subjects--Topical Terms: </label><br/>Systems
<br/><br/><label>Dewey Class. No.: </label>003  / ENC