University of Cambridge. (2014). Cambridge key English test 6 with answers: Authentic examination papers from Cambridge ESOL. Việt Nam: Fahasa Printing Factory.

University of Cambridge. Cambridge Key English Test 6 With Answers: Authentic Examination Papers From Cambridge ESOL. Việt Nam: Fahasa Printing Factory, 2014.

University of Cambridge. Cambridge Key English Test 6 With Answers: Authentic Examination Papers From Cambridge ESOL. Việt Nam: Fahasa Printing Factory, 2014.