England, Alan
Macmillan Education, 1990
Buku Teks
edited by Julian Hilton
Macmillan, 1993
Buku Teks
editor, James R. Brandon
Cambridge Unipersity Press, 1993
Buku Referensi
Arnold, Stephanie, author
Mayfield Publishing Company, 2001
Buku Teks
Elam, Keir, author
Methuen, 1980
Buku Teks