Schmidt, Steven
Prentice-Hall, 1983
Buku Teks
Slade, Catharine
Pageone, 2002
Buku Referensi
Quinn, Gerard
Studio Editions, 1990
Buku Referensi
Bland, David
Faber and Faber LimIted, 1969
Buku Teks
Black Book Marketing Group
Black Book Marketing Group, 1995
Buku Teks