@book{2979,
	author = {Barnett, Raymond A. and Ziegler, Michael R.},
	title = {College algebra with trigonometry.},
	publisher = {McGraw-Hill,},
	year = {c2001.},
	series = {Barnett, Ziegler & Byleen's precalculus series},
	address = {Boston :},
	edition = {7th ed. /},
	note = {Includes indexes.},
	url = {https://marinazahara22.wordpress.com/wp-content/uploads/2013/10/college_algebra_with_trigonometry.pdf}
}