Ruth Gairns. (2003). Natural english (upper- intermediate student's book). Oxford, NY: Oxford Univ. Press.
Chicago Style aipamenaRuth Gairns. Natural English (upper- Intermediate Student's Book). Oxford, NY: Oxford Univ. Press, 2003.
MLA aipamenaRuth Gairns. Natural English (upper- Intermediate Student's Book). Oxford, NY: Oxford Univ. Press, 2003.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.