@book{217988,
	author = {Lipschutz, Seymour. and Lipson, Marc.},
	title = {2000 solved problems in discrete mathematics /},
	publisher = {McGraw-Hill,},
	year = {c1992.},
	address = {New York :},
	url = {http://www.loc.gov/catdir/enhancements/fy1012/91014108-b.html}
}