Williams, Howard
St. Martin`s Press, 1996
Buku Teks SO
Schippers, Birgit, author
Routledge, 2014
Buku Teks SO
Buzan, Barry
Cambridge University Press, 2015
Buku Teks
Sheldon Anderson ... [and others]
Westview Press, 2015
Buku Teks SO
Berridge, G.R.
Palgrave Macmillan, 2015
Buku Teks SO