@book{17317,
	author = {Sarama, Julie and Clements, Douglas H.},
	title = {Early childhood mathematics education research},
	publisher = {Routledge,},
	year = {2009},
	series = {Studies in mathematical thinking and learning},
	address = {New York :},
	url = {http://www.netlibrary.com  .libraryumpsa.idm.oclc.org/urlapi.asp?action=summary&v=1&bookid=267002}
}