Michal Shmueli-Scheuer Chen Li Yosi Mass Haggai Roitman Ralf Schenkel Gerhard Weikum Best-Effort Top-k Query Processing Under Budgetary Constraints. 928-939 2009 ICDE http://doi.ieeecomputersociety.org/10.1109/ICDE.2009.109 conf/icde/2009 db/conf/icde/icde2009.html#Shmueli-ScheuerLMRSW09