Close, R.A.
Longmans , 1967
Buku Teks
Murphy, Raymond, author
Cambridge University Press, 1998
Buku Teks
McKay, Herbert
Oxford University Press, 1948
Buku Teks
Thornley, G. C.
Longman Group Limited, 1970
Buku Teks
West, Michael
Longmans, Green and Co., 1951
Buku Teks