Duckworth, M. (1996). Open doors: Workbook 3. Oxford: Oxford University Press.
Chicago Style aipamenaDuckworth, Michael. Open Doors: Workbook 3. Oxford: Oxford University Press, 1996.
MLA aipamenaDuckworth, Michael. Open Doors: Workbook 3. Oxford: Oxford University Press, 1996.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.