Sudipto Das Divyakant Agrawal Amr El Abbadi CAM conscious integrated answering of frequent elements and top-k queries over data streams. 1-10 2008 DaMoN http://doi.acm.org/10.1145/1457150.1457152 conf/damon/2008 db/conf/damon/damon2008.html#DasAA08