Swan, Michael
The new Cambridge English course. Student 4, Upper-intermediate
Cambridge University Press, 1993
Buku Teks SO
English for economics
Buku Teks
Brown, E.H. Phelps
A Course in applied Economics
Sir Isaac Pitman & Sons, 1953
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Low, Ona
Proficiency in english course
Edward Arnold, 1986
Buku Teks SO
Ewer, J.R.
A course in basic scientific English
Longman, 1969
Buku Teks SO