@InProceedings{plaxton07online, 
author = {G. Plaxton and M. Tiwari and P. Yalagandula}, 
 title = {Online Aggregation over Trees}, 
 booktitle = {Proceedings of the 21 st International Parallel and Distributed Processing Symposium (IPDPS)}, 
 year = 2007 , 
 month = Mar, 
 category = "sdims,webos" 
 }