@unpublished{publication-5718,
	author={Engelmann, Dirk and Fischbacher, Urs},
	institution={University of Zurich},
	issn={1424-0459},
	number={No. 132},
	series={Working paper series / Institute for Empirical Research in Economics},
	title={Indirect Reciprocity and Strategic Reputation Building in an Experimental Helping Game},
	year=2002,
}