Adams, Kristen David
St. Paul, MN : West Group, 2010
Buku Teks
Macintryre, Ewan
Blackstone Press, 1998
Buku Referensi
Stephenson, Graham
Blakstone Press, 1995
Buku Teks
West Publishing Co., 1993
Buku Referensi
Braucher, Robert
Foundation Press, 1958
Buku Teks