References Alcalde-Unzu, J. and E. Molis. Exchange of indivisible goods and indifferences: Absorbing Sets mechanisms. Games and Economic Behavior, 73(1):1-16, 2011. Ashlagi, I. and A. E. Roth. New challenges in multi-hospital kidney exchange. American Economic Review Papers and Proceedings, 102 (3): 354-359, 2012. Ashlagi, I. and A. E. Roth. Free riding and participation in large scale, multi-hospital kidney exchange. Forthcoming, Theoretical Economics, 2013. Ausubel, L. M. and T. Morrill. Sequential kidney exchange, 2013. Forthcoming, American Economic Journal: Microeconomics, 2013 Bird, C. G. Group incentive compatibility in a market with indivisible goods. Economics Letters, 14(4): 309- 313, 1984. Bogomolnaia, A. and H. Moulin. A simple random assignment problem with a unique solution. Economic Theory, 19(3): 623-636, 2002. Chung, K. On the existence of stable roommate matchings. Games and Economic Behavior, 33: 206-230, 2000. Delmonico, F. L. Exchanging kidneys: Advances in living-donor transplantation. The New England Journal of Medicine, 350: 1812- 1814, 2004. Delmonico, F. L., G. S. Lipkowitz, P. E. Morrissey, J. S. Stoff, J. Himmelfarb, W. Harmon, M. Pavlakis, H. Mah, J. Goguen, R. Luskin, E. Milford, G. B. M. Chobanian, B. Bouthot, M. Lorber, and R. J. Rohrer. Donor kidney exchanges. American Journal of Transplantation, 4: 1628-1634, 2004. Ehlers, L. Coalitional strategy-proof house allocation. Journal of Economic Theory, 105(2): 298- 317, 2002. Gentry, S. E., D. L. Segev, M. Simmerling, and R. A. Montgomery. Expanded kidney paired donation through participation by compatible pairs. American Journal of Transplantation, 7: 99-107, 2007. Gjertson, D. W. Explainable variation in renal transplant outcomes: A comparison of standard and expanded criteria donors. Clinical Transplants, 2004: 303- 314, 2004. Gjertson, D. W. and J. Cecka. Living unrelated donor kidney transplantation. Kidney International, 58: 491-499, 2000. HatffieldJ. W. Pairwise kidney exchange: Comment. Journal of Economic Theory, 125: 189- 193, 2005. Hylland, A. and R. Zeckhauser. The efficient allocation of individuals to positions. Journal of Political Economy, 87: 293-314, 1979. Jaramillo, P. and V. Manjunath. The difference indifference makes in strategy-proof allocation of objects. Journal of Economic Theory, 147: 1913-1946, 2012. Keizer, K., M. de Klerk, B. Haase-Kromwijk, and W. Weimar. The Dutch algorithm for allocation in living donor kidney exchange. Transplantation Proceedings, 37:589- 591, 2005. Ma, J. Strategy-proofness and the strict core in a market with indivisibilities. International Journal of Game Theory, 23: 75-83, 1994. Miyagawa, E. Strategy-proofness and the core in house allocation problems. Games and Economic Behavior, 38(2): 347-361, 2002. NHS Blood and Transplant. National matching scheme for paired and pooled (kidney) donation, 2009. http://www.organdonation.nhs.uk. Nicolò, A. and C. Rodríguez-Álvarez. Transplant quality and patients' preferences in paired kidney exchange. Games and Economic Behavior, 74(1): 299-310, 2012. Oien, C. M., A. V. Reisaeter, T. Leivestad, F. W. Dekker, P. D. Line, and I. Os. Living donor kidney transplantation: The e_ects of donor age and gender on shortand long-term outcomes. Transplantation, 83(5): 600-606, 2007. Opelz, G. Impact of HLA compatibility on survival of kidney transplants from unrelated live donors. Transplantation, 64: 1473-1475, 1997. Opelz, G. for the Collaborative Transplant Study. Hla compatibility and kidney grafts transplants from unrelated live donors. Transplantation Proceedings, 30:704-705, 1998. Organización Nacional de Transplantes. Programa nacional de donación renal cruzada en España. Technical report, Documentos de Consenso ONT, September 2009. Pápai, S. Strategy-proof single unit award rules. Social Choice and Wefare, 18(4): 785-798, 2001. Park, K., J. Lee, K. Huh, S. Kim, and Y. Kim. Exchange living-donor kidney transplantation: Diminution of donor organ shortage. Transplantation Proceedings, 36: 2949-2951, 2004. Rees, M. A., J. E. Kopke, R. P. Pelletier, D. L. Segev, M. E. Rutter, A. J. Fabrega, J. Rogers, O. G. Pankewycz, J. Hiller, A. E. Roth, T. Sandholm, M. U. Ünver, and R. A. Montgomery. A nonsimultaneous, extended, altruistic-donor chain. The New England Journal of Medicine, 360: 1096-1101, 2009. Roth, A. E. Incentive compatibility in a market with indivisible goods. Economics Letters, 9: 127-132, 1982. Roth, A. E., T. Sönmez, and M. U. Ünver. Kidney exchange. Quarterly Journal of Economics, 119: 457-488, 2004. Roth, A. E., T. Sönmez, and M. U. Ünver. Pairwise kidney exchange. Journal of Economic Theory, 125:151{188, 2005. Roth, A. E., T. Sönmez, and M. U. Ünver. A kidney exchange clearinghouse in New England. American Economic Review, Papers and Proceedings, 95: 376-380, 2005. Roth, A. E., T. Sönmez, and M. U. Ünver., F. L. Delmonico, and S. L. Saidman. Utilizing list exchange and nondirected donations through chain-paired kidney donations. American Journal of Transplantation, 6: 2694- 2705, 2006. Roth, A. E., T. Sönmez, and M. U. Ünver. Efficient kidney exchange: Coincidence of wants in a markets with compatibility preferences. American Economic Review, 97(3):828-851, 2007. Shapley, L. and H. Scarf. On cores and indivisibility. Journal of Mathematical Eco nomics, 1: 23-37, 1974. Sönmez, T. Strategy-proofness and essentially single-valued cores. Econometrica, 67: 677-689, 1999. Sönmez, T. and M. U. Ünver. Altruistically unbalanced kidney exchange. Unpublished Manuscript, Boston College, 2013. Su, X., S. A. Zenios, and G. M. Chertow. Incorporating recipient choice in kidney transplantation. Journal of the American Society of Nephrology, 15: 1656-1663, 2004. Svensson, L.-G. Strategy{proof allocation of indivisible goods. Social Choice and Welfare, 16(4): 557-567, 1999. Ünver, M.U. Dynamic kidney exchange. Review of Economic Studies, 77: 372-414, 2010. Yilmaz, Ö. Kidney exchange: An egalitarian mechanism. Journal of Economic Theory, 146: 592-618, 2011. Yilmaz, Ö. Kidney exchange: Further utilization of donors via listed exchange. Forthcoming Journal of Mathematical Economics, 2013. Zenios, S. A. Optimal control of a paired-kidney exchange program. Management Science, 48: 328-342, 2002.