Britannica:   Book of the year 1968 
/ Encyclopeadia Britannica, Inc. 
 - Chicago:   Encyclopeadia Britannica, Inc.,   1968 
 - 832p. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Reference work
<br/><br/><label>Subjects--Index Terms: </label>Encyclopeadia 
<br/><br/><label>Universal Decimal Class. No.: </label>R 030.1  / K8