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