O'Connell, S. (1989). Focus on proficiency. Collings: London and Galasgow.
Chicago Style aipamenaO'Connell, Sue. Focus On Proficiency. Collings: London and Galasgow, 1989.
MLA aipamenaO'Connell, Sue. Focus On Proficiency. Collings: London and Galasgow, 1989.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.