Antonios Deligiannakis Yannis Kotidis Vassilis Stoumpos Alex Delis Building Efficient Aggregation Trees for Sensor Network Event-Monitoring Queries. 63-76 2009 GSN http://dx.doi.org/10.1007/978-3-642-02903-5_7 conf/gsn/2009 db/conf/gsn/gsn2009.html#DeligiannakisKSD09