APA (7th ed.) Citation

(1992). The World Book Encyclopedia: Volume 21 ( W.X-Y.Z ). World Book, Inc..

Chicago Style (17th ed.) Citation

The World Book Encyclopedia: Volume 21 ( W.X-Y.Z ). London: World Book, Inc., 1992.

MLA (9th ed.) Citation

The World Book Encyclopedia: Volume 21 ( W.X-Y.Z ). World Book, Inc., 1992.