Robison, Richard, 1943-, author
Routledge, 2004
Buku Teks
Hammer, Darrel P.
Westview Press, 1990
Buku Teks
Rivoli, Pietra, author
John Wiley & Sons, 2005
Buku Teks
Wiarda, Howard J., author
Hartcourt College Publishers, 2001
Buku Teks
Beer, Samuel H., author
Alfred A. Knopf, 1966
Buku Teks