The British Council
The British Council, 1999
Buku Teks
Southwell, E.A., author
Longmans, Green, 1947
Buku Teks
Emsley, John, author
W.H. Freeman Spektrum , 1994
Buku Referensi
Korea Foundation
Cookand/Besthome, 2003
Buku Teks
Peters, Pam, author
Cambridge University Press, 2006
Buku Referensi