University of Cambridge. (2008). Key English test extra with answers: Official examination papers from University of Cambridge ESOL Examinations. New York: Cambridge university press.
Stile di citazione ChicagoUniversity of Cambridge. Key English Test Extra With Answers: Official Examination Papers From University of Cambridge ESOL Examinations. New York: Cambridge university press, 2008.
Citazione MLAUniversity of Cambridge. Key English Test Extra With Answers: Official Examination Papers From University of Cambridge ESOL Examinations. New York: Cambridge university press, 2008.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.