Robert M. Bell Yehuda Koren Scalable Collaborative Filtering with Jointly Derived Neighborhood Interpolation Weights. 43-52 2007 ICDM http://doi.ieeecomputersociety.org/10.1109/ICDM.2007.90 conf/icdm/2007 db/conf/icdm/icdm2007.html#BellK07