@unpublished{publication-5523,
	author={Frey, Bruno S and Torgler, Benno},
	institution={University of Zurich},
	issn={1424-0459},
	number={No. 286},
	series={Working paper series / Institute for Empirical Research in Economics},
	title={Tax Morale and Conditional Cooperation},
	year=2006,
}