Markus M. Breunig Hans-Peter Kriegel Peer Kröger Jörg Sander Data Bubbles: Quality Preserving Performance Boosting for Hierarchical Clustering. 79-90 2001 SIGMOD Conference db/conf/sigmod/sigmod2001.html#BreunigKKS01 http://doi.acm.org/10.1145/375663.375672 http://www.acm.org/sigs/sigmod/sigmod01/eproceedings/papers/Research-Breunig-et-al.pdf