APA (7th ed.) Citation
World Book, Inc. (2004). The World Book Encyclopedia: Volume -21. World Book, Inc.
Chicago Style (17th ed.) Citation
World Book, Inc. The World Book Encyclopedia: Volume -21. Chicago: World Book, Inc, 2004.
MLA (9th ed.) Citation
World Book, Inc. The World Book Encyclopedia: Volume -21. World Book, Inc, 2004.
Warning: These citations may not always be 100% accurate.