APA (7th ed.) Citation

(2013). The world book encyclopedia volume 21 - W-X-Y-Z. World Book.

Chicago Style (17th ed.) Citation

The World Book Encyclopedia Volume 21 - W-X-Y-Z. Chicago: World Book, 2013.

MLA (9th ed.) Citation

The World Book Encyclopedia Volume 21 - W-X-Y-Z. World Book, 2013.

Warning: These citations may not always be 100% accurate.