Low, Ona
Proficiency in english course
Edward Arnold, 1986
 Buku Teks SO
Stone, Linton
Cambridge proficiency English / Linton Stone
Macmillan, 1967
 Buku Teks SO
Sewell, R.
India before the English / R. Sewell
Asian Educational Services, 1987
 Buku Teks SO
Dieterich, Thomas G.
A linguistic guide to english proficiency testing in schools / Thomas G. Dieterich and Cecilia Freeman
Center for Applied Linguistics, 1979
 Buku Teks
Derolez, R.
Runica manuscripta : the English tradition / R. Derolez
De Tempel, 1954
 Buku Teks