Littleton, A.C.
Prentice-Hall, 1962
Buku Teks
Abramson, Paul R.
A Division of Congressional Quarterly, 1986
Buku Teks
Maraini, Fosco
Kodansha AInternational, 1983
Buku Teks
Cobb, Nancy J.
Mayfield Publishing, 2000
Buku Teks
Casper, Lynne M.
Sage, 2000
Buku Teks