Beijing Kexue Chubanshe 1988
Buku Referensi
Far East Book Co., 1985
Buku Referensi
Macmillan, 2002
Buku Referensi
Crawley, Angela, author
Oxford University Press, 2000
Buku Referensi
Hornby, Albert Sydney, author
Oxford University Press, 1991
Buku Referensi