Ufflen, Chris van
Offices
Braun, 2013
 Buku Teks SO
There is another China
King's Crown Press, 1948
 Buku Teks SO
Withing offices
Cheng, Kalley, editorial director
New York : Page One, 2004,
 Buku Referensi
Within offices
Page one Publishing , 2003
 Buku Referensi
Nation, I.S.P.
Learning vocabulary in another language
Cambridge University Press, 2013
 Buku Teks SO