APA (7th ed.) Citation
(1991). <The> World Book Encyclopedia (9. ed.). World Book.
Chicago Style (17th ed.) Citation
<The> World Book Encyclopedia. 9. ed. Chicago: World Book, 1991.
MLA (9th ed.) Citation
<The> World Book Encyclopedia. 9. ed. World Book, 1991.
Warning: These citations may not always be 100% accurate.