(2001). The World book encyclopedia: W-X-Y-Z V.21. World book, Inc.
Chicago Style aipamenaThe World Book Encyclopedia: W-X-Y-Z V.21. World book, Inc, 2001.
MLA aipamenaThe World Book Encyclopedia: W-X-Y-Z V.21. World book, Inc, 2001.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.