Croarken, Mary, author
Clarendon Press, 1990
Buku Teks
edited by Maurice Mullard
Routledge, 1995
Buku Teks
Artikel Jurnal
Ben Jackson, Robert Saunders, editors
Cambridge University Press, 2012
Buku Teks
Peacock, H.L., author
Heinemann Educational Books, 1980
Buku Teks