editor, James R. Brandon
Cambridge Unipersity Press, 1993
Buku Referensi
Vogel, Harold L., author
Cambridge University Press, 2007
Buku Teks
RoutledgeCurzon, 2005
Buku Teks
Tait, Viola
Heinemann, 1970
Buku Teks
Peters, Pam, author
Cambridge University Press, 2006
Buku Referensi