Peter Salim, author
Modern English Press, 1993
Buku Referensi
Greener, Michael, author
Penguin books, 1994
Buku Referensi
Pass, Chirtopher, author
Erlangga, 1997
Buku Referensi
Collin, P. H., author
Peter Collin Publishing, 2001
Buku Teks
De Vries, Mary Ann, author
Prentice-Hall, 1995
Buku Referensi