Exchange in a general market with indivisible goods

We examine general exchange markets with heterogenous indivisible goods, where each agent may be endowed with a set of indivisible goods, but there is no divisible good that could be used as a medium of exchange. Thus, our model is a generalization of the Shapley-Scarf housing market model, in which each agent owns one indivisible good. Our main result is a characterization of the set of group-strategyproof and individually rational exchange rules that satisfy a mild eeciency requirement.