Cambridge IELTS 7: examination papers from University of Cambridge ESOL examinations: english for speakers of other language
Cambridge University Press, 2009
 Buku Teks
McCarthy, Michael
Touhstone
Cambridge, 2006
 Buku Teks
Cambridge IELTS with answers edition : examination papers from university of cambridge ESOL examinations
Cambridge University
Cambridge university press, 2000
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Pollock, Carroll Washington
Communicate what you mean : grammar for high level ESL students / Carroll Washington Pollock
Prentice-Hall, 1982
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Fries, Charles Carpenter
Teaching and learning english as a foreign language
University of Michigan Press, 1951
 Buku Teks SO