Artikel Jurnal
Schulz, Ernest B
[publisher not identified], 1956
Buku Teks
Arblaster, Anthony, author
Open University Press, 1987
Buku Teks
by William Ebenstein [and others]
Harper & Row, Publishers, 1970
Buku Teks
edited by Francis Loh Kok Wah
Curzon Press, 2002
Buku Teks