Jones, L. (1993). Progress to Proficiency: Student's Book (New edition.). Cambridge: Cambridge University Press.
Chicago Style aipamenaJones, Leo. Progress to Proficiency: Student's Book. New edition. Cambridge: Cambridge University Press, 1993.
MLA aipamenaJones, Leo. Progress to Proficiency: Student's Book. New edition. Cambridge: Cambridge University Press, 1993.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.