@unpublished{publication-5350,
	author={Akkoyunlu, Sule and Lichtenberg, Frank R and Siliverstovs, Boriss and Zweifel, Peter},
	institution={University of Zurich},
	number={No. 903},
	series={Working paper series / Socioeconomic Institute},
	title={Spurious correlation in estimation of the health production function: A note},
	year=2009,
}