Sudhir Kumar Singh Vwani P. Roychowdhury Himawan Gunadhi Behnam Attaran Rezaei Capacity Constraints and the Inevitability of Mediators in Adword Auctions. 318-325 2007 conf/wine/2007 WINE http://dx.doi.org/10.1007/978-3-540-77105-0_33 db/conf/wine/wine2007.html#SinghRGR07