Blamires, Harry, author
Longman, 1989
Buku Teks
Evans, B. Ifor
Penguin Books, 1944
Buku Teks
edited by David Graddol, Dick Leith and Joan Swann
Routledge , 2000
Buku Teks
Needleman, Morris H., author
Barnes & Noble, 1939
Buku Teks
Otis, William Bradley, author
Barnes & Noble, 1939
Buku Teks