Doff, Adrian, author
Cambridge University Press, 2010
Multimedia
edited by Michael Swan and Bernard Smith
Cambridge University Press, 1987
Buku Teks
Regional English Language Office (RELO), 2009
Buku Referensi
Tucker, T.G.
Macmillan, 1923
Buku Teks
Baker, Ann, author
Cambridge University Press, 1982
Buku Teks