@unpublished{publication-5207,
	author={Berentsen, Aleksander and Marchesiani, Alessandro and Waller, Christopher J},
	institution={University of Zurich},
	issn={1424-0459},
	number={No. 517},
	series={Working paper series / Institute for Empirical Research in Economics},
	title={Channel Systems: Why is there a Positive Spread?},
	year=2010,
}