@book{7396,
	author = {Ensley, Douglas E. and Crawley, J. Winston.},
	title = {Discrete mathematics : mathematical reasoning and proof with puzzles, patterns, and games},
	publisher = {Wiley,},
	year = {c2006.},
	address = {Hoboken, NJ :},
	url = {http://www.loc.gov/catdir/toc/ecip0514/2005017417.html}
}