Aris Ananta, author
ISEAS, 2005
Buku Teks
Arblaster, Anthony, author
Open University Press, 1987
Buku Teks
Schulz, Ernest B
[publisher not identified], 1956
Buku Teks
Catt, Helena, author
Routledge , 1999
Buku Teks
Mackie, Gerry, author
Cambridge University Press, 2003
Buku Teks