Themistoklis Palpanas Richard Sidle Roberta Cochrane Hamid Pirahesh Incremental Maintenance for Non-Distributive Aggregate Functions. 2002 conf/vldb/2002 VLDB db/conf/vldb/vldb2002.html#PalpanasSCP02 http://www.vldb.org/conf/2002/S22P04.pdf 802-813