Office of the Secretary of State for Information and Tourism, [date of publication not identified]
Buku Teks
Oxford University Press, 1953
Buku Teks
Andrews, Jonathan; Briggs, Asa; Porter, Roy; Tucker, Penny; Waddington, Keir
Routledge, 1997
Buku Referensi
Rothstein, Andrew, author
Penguin Books , 1950
Buku Teks
Fry, Peter Somerset, author
Routledge , 2001
Buku Teks