Splinter, John P.
Zondervan Publishing House, 1992
Buku Referensi
Rich, Phil
John Wiley & Sons, 2000
Buku Teks SO
Sinclair, Ian R.
Newnes Butterworth-Heinemann, 1994
Buku Teks
edited by Matt Bonass, Michael Rudd
Globe Law and Business, 2010
Buku Teks
edited by Joseph S. Wholey
Jossey-Bass Publishers, 1994
Buku Teks