@book{5949,
	author = {Card, David E. and ebrary, Inc.},
	title = {Small differences that matter},
	publisher = {University of Chicago Press,},
	year = {c1993.},
	series = {NBER Comparative labor markets series},
	address = {Chicago :},
	url = {http://site.ebrary.com/lib/rucke/Doc?id=10275458}
}