Bennison, George Mills, author
Routledge, 2013
Buku Teks
Powell, Derek, author
Harlow Longman, 1994
Buku Teks
Powell, Derek, author
Longman, 1992
Buku Teks
Johnson, W. E., author
Edward Arnold, 1971
Buku Teks
Butler, B.C.M., author
Longman Scientific & Technical , 1988
Buku Teks