Hewings, Martin, author
Cambridge University Press, 2006
Buku Teks
Hewings, Martin, author
Cambridge University Press, 2005
Buku Teks
Muhibbin Syah, author
RajaGrafindo Persada, 2010
Buku Teks
McCarthy, Michael, author
Erlangga, 2002
Buku Teks
Azar, Betty Schrampfer, 1941-, author
Prentice Hall Regents, 1989
Buku Referensi