@book{26856,
	author = {Van de Walle, John A. and Karp, Karen,},
	title = {Elementary and middle school mathematics teaching developmentally/},
	publisher = {Pearson/Allyn and Bacon Publishers,},
	year = {2010.},
	address = {Boston :},
	edition = {7th ed.},
	url = {http://www.loc.gov/catdir/toc/ecip0828/2008040112.html}
}