Ashraf Al Daoud Murat Alanyali David Starobinski Reservation policies for revenue maximization from secondary spectrum access in cellular networks. 288-294 2010 WiOpt http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5518800 conf/wiopt/2010 db/conf/wiopt/wiopt2010.html#DaoudAS10