Collier, Abram T., author
Harper & Row, 1962
Buku Teks
Wilbur
Harper ,
Buku Teks
Powell, Gary N.
Sage Publications, 1988
Buku Teks
Drucker, Peter F. (Peter Ferdinand), 1909-2005, author
Harper Colophan Books, 1977
Buku Teks
Donaldson, Gordon
Double day, 1985
Buku Teks