Blackwell Publishing,
Majalah, Jurnal, Buletin
Whittaker, David J.
Routledge, 2004
Buku Teks
Jane's Information Group, 1999
Buku Referensi
Toynbee, Arnold J.
Oxford University Press, 1957
Buku Teks SO
edited by Lois Beck and Nikki Kiddie
Harvard University Press, 1978
Buku Teks SO