Fox, Michael W.
The Lyons Press, 1999
Buku Teks
Fox, Michael W.
University Park Press, 1983
Buku Teks
New York : macmillan Library reference USA, 1997,
Buku Referensi
Begon, Michael, author
Sinauer Associates, 1986
Buku Teks
Drucker, Peter F. (Peter Ferdinand), 1909-2005, author
Truman Talley Books/Plume, 1992
Buku Teks