Beck, Ulrich
Malden, MA :Polity Press, 2005
Buku Teks SO
Ellsworth, P.T.
Macmillan, 1975
Buku Teks SO
Vernon, Raymond
Prentice-Hall, 1981
Buku Teks
Balaam, David N., 1950-
Pearson/Prentice Hall, 2005
Buku Teks SO
Balaam, David N., 1950-
Prentice-Hall, 1996
Buku Teks SO