(2000). The World of learning, 2001 (51st ed.). Europa Publications.
Chicago Style aipamenaThe World of Learning, 2001. 51st ed. London: Europa Publications, 2000.
MLA aipamenaThe World of Learning, 2001. 51st ed. Europa Publications, 2000.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.