2O' Brien, D. P. and Shaffer, G. : 1997, Nonlinear supply con- tracts, exclusive dealing, and equilibrium market foroclosure, Journal of Economics & Management Strategy.
3Schneller, E. S. : 2005, The value of group purchasing in the heathecare supply chain, Arizona State University, School of Health Man- agement and Policy.
4Sethi, S. P. : 2006, Group purchasing organizations: An evalua- tion of their effectiveness in providing services to hospitals and their pa- tients, Report No. ICCA - 2006. G - 01, www. ICCA - corporatedac- countability, org.
5Dana, J. : 2003, Buyer groups as strategic commitments, Working paper. Northwestern University.
6Burns, L. R. and Lee, J. A. : 2008, Hospital purchasing alli- ances: Utilization, services, and Performance, Health Care Management Review 33, 203 -215.
7Chen, R. R. and Roma, P. : 2008, Group - buying of competing retailers, Working paper. University of California at Davis.
8Marvel, H. P. and Yang, H. : 2008, Group purchasing, nonlinear tariffs, and oligopoly, International Journal of Industrial Organization.