Ramsden, Paul
Routledge , 1992
Buku Teks
edited by Michael Byram
Multilingual Matters, 1994
Buku Teks SO
Brown, George
Routledge, 1997
Buku Teks
edited by Heather Fry, Steve Ketteridge and Stephanie Marshall
Routledge, 2009
Buku Referensi
Rockart, John Fralick
McGraw-Hill, 1975
Buku Teks