@book{75551,
	author = {Twisk, Jos W. R.,},
	title = {Applied multilevel analysis :},
	publisher = {Cambridge University Press,},
	year = {2006 [6th printing 2013]},
	address = {Cambridge, UK ;},
	url = {http://www.loc.gov/catdir/enhancements/fy0702/2006299215-d.html}
}