West Publishing Co, 1993
Buku Referensi
Rodgers, William H., author
St. Paul Minn, 1977
Buku Teks
Bockrath, Joseph T.
McGraw-Hill, 1977
Buku Teks
Little,Brown and Company, [date of publication not identified]
Buku Teks
Tabb, William Murray
The Michie Company, 1992
Buku Teks