@book{58625,
	author = {Cohen, David and Lee, Theodore},
	title = {Precalculus with unit-circle trigonometry /},
	publisher = {Thomson Brooks/Cole,},
	year = {c2006},
	address = {Belmont, CA :},
	edition = {4th ed.},
	url = {http://www.loc.gov/catdir/enhancements/fy1103/2005921577-t.html}
}