Reynolds, P.A.
Longman, 1994
Buku Teks SO
Couloumbis, Theodore A.
Prentice-Hall, 1990
Buku Teks SO
Pearson, Frederic S.
McGraw-Hill, 1992
Buku Teks SO
edited by John Baylis and Steve Smith
Oxford University Press, 2006
Buku Teks SO
Griffith, Martin
Routledge, 2002
Buku Teks