Saharon Rosset Claudia Perlich Yan Liu Making the most of your data: KDD Cup 2007 "How Many Ratings" winner's report. 66-69 2007 9 SIGKDD Explorations 2 http://doi.acm.org/10.1145/1345448.1345463 db/journals/sigkdd/sigkdd9.html#RossetPL07