UNESCO. (1999). Adult learning and the challenges of the 21st century. UNESCO.
Chicago Style aipamenaUNESCO. Adult Learning and the Challenges of the 21st Century. Germany: UNESCO, 1999.
MLA aipamenaUNESCO. Adult Learning and the Challenges of the 21st Century. UNESCO, 1999.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.