APA Citation

(1990). The world book encyclopedia: Volume 21 (W - X - Y - Z). U.S.A: World Book Inc..

Chicago Style Citation

The World Book Encyclopedia: Volume 21 (W - X - Y - Z). U.S.A: World Book Inc., 1990.

MLA Citation

The World Book Encyclopedia: Volume 21 (W - X - Y - Z). U.S.A: World Book Inc., 1990.

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