Oxford University Press , 1992
Buku Teks
Bullis, L. Harold
Westview Press, 1985
Buku Teks
Bullis, L. Harold
Westview Press, 1985
Buku Teks
L Etang, Jacquie
International Thomson Business Press , 1996
Buku Teks
Fairclough, Norman, author
Longman, 1997
Buku Teks