Vogel, Harold L.
Cambridge University Press, 2007
Buku Teks
RoutledgeCurzon, 2005
Buku Teks
Tait, Viola
Heinemann, 1970
Buku Teks
Peters, Pam
Cambridge University Press, 2006
Buku Referensi
Cotterill, Rodney
Cambridge University Press, 1989
Buku Referensi