Burton, William C.
New York : Macmillan, 1992,
Buku Referensi
Gubby, Helen
Boon Juridische Uitgevers, 2007
Buku Teks
Beatty, Jeffrey F.
South Western Cengage Learning, 2011
Buku Teks
Haigh, Rupert
Routledge-Cavendish, 2009
Buku Teks
Brown, Gordon W.
Prentice-Hall, 1990
Buku Referensi