@book{9071,
	author = {Williams, H. P.},
	title = {Model building in mathematical programming /},
	publisher = {Wiley,},
	year = {1999.},
	address = {Chichester ;},
	edition = {4th ed.},
	url = {http://www.loc.gov/catdir/description/wiley0310/99032311.html}
}