Powell, Derek, author
Longman, 1992
Buku Teks
Powell, Derek, author
Harlow Longman, 1994
Buku Teks
Butler, B.C.M., author
Longman Scientific & Technical , 1988
Buku Teks
Bennison, George Mills, author
Routledge, 2013
Buku Teks
Anderson, Franz E., author
Burgess Publishing, 1979
Buku Teks