Improving rating estimation in recommender systems using aggregation- and variance-based hierarchical models.

Akhmed Umyarov Alexander Tuzhilin Improving rating estimation in recommender systems using aggregation- and variance-based hierarchical models. 37-44 2009 RecSys http://doi.acm.org/10.1145/1639714.1639722 conf/recsys/2009 db/conf/recsys/recsys2009.html#UmyarovT09