@book{13504,
	author = {Koepsell, Thomas D. and Weiss, Noel S.,},
	title = {Epidemiologic methods :},
	publisher = {Oxford University Press,},
	year = {2003.},
	address = {Oxford ;},
	url = {http://www.loc.gov/catdir/toc/fy041/2002033763.html}
}