Pricewaterhouse coopers, 2011
Buku Referensi
Folsom, Ralph Haughwout, author
St. Paul, Minn, 1995
Buku Teks
Folsom, Ralph Haughwout, author
West Group, 1996
Buku Teks
Folsom, Ralph Haughwout, author
West Publishing, 1992
Buku Teks
Tillinghast, David R., author
Matthew Bender, 1984
Buku Teks