(1990). Headway: Advanced (Student's book). Oxford: Oxford Univ. Press.
Chicago Style aipamenaHeadway: Advanced (Student's Book). Oxford: Oxford Univ. Press, 1990.
MLA aipamenaHeadway: Advanced (Student's Book). Oxford: Oxford Univ. Press, 1990.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.