Garfield, Simon
Faber , 1994
Buku Teks
edited by Richard Haigh, Dai Harris
Routledge, 1994
Buku Teks
Her Majesty's Stationery Office, 1955
Buku Teks
Bromhead, Peter
Longman, 1992
Buku Teks
Cambridge Independence Educational Publishers 1994,
Buku Teks