Macmillan, 1996
Buku Referensi
Messinger, Heinz, author
Langenscheidt, 1993
Buku Referensi
Garland, Henry, author
Oxford University Press, 1995
Buku Referensi
Delair Publishing Company, 1981
Buku Referensi
The World Publishing Co., 1960
Buku Referensi