@book{228127,
	author = {Koba, Susan. and Mitchell, Carol T. and ebrary, Inc.},
	title = {Hard-to-teach science concepts},
	publisher = {National Science Teachers Association,},
	year = {c2011.},
	address = {Arlington, Va. :},
	url = {http://site.ebrary.com/lib/rucke/Doc?id=10492835}
}