edited by Andrew Blowers, Bob Evans
Routledge, 1997
Buku Teks SO
Trident Press, [Date of publication not identified]
Buku Referensi
Ward, Ralph D.
John Wiley & Sons, 1997
Buku Teks SO
Yablonsky, Lewis
Wadsworth, 2000
Buku Teks
Nugent William R.
Thomson Learning, 2001
Buku Teks