Kissler, Gary D.
Addison-Wesley, 1991
Buku Referensi
Cooper, Wendy
Hutchinson , 1975
Buku Teks
Open University Press, 1998
Buku Teks
Dolbeare, Kenneth M.
D.C. Heath, 1985
Buku Teks
edited by G. John Ikenberry
Cambridge University Press, 2014
Buku Teks