Voiles, Price R.
Business English essentials
Glencoe, 1993
 Buku Teks SO
French, F. G.
Self-help exercises for practice in English; Book III
Oxford University Press, 1947
 Buku Teks SO
Thornley, G. C.
Easier scientific English practice / G. C. Thornley
Longman Group Limited, 1970
 Buku Teks SO
Graver, B.D.
Advanced english practice
Walton Street , 1987
 Buku Teks SO
Drummond, Gordon
English sentence patterns and multi-level practice exercises with grammar notes
Essex Longman, 1972
 Buku Teks SO