title: a robust , optimization-based approach for approximate answering of aggregate queries. authors: vivek r. narasayya , gautam das , surajit chaudhuri. venue: sigmod conference. year: 2001
title: the aqua approximate query answering system. authors: swarup acharya , phillip b. gibbons , viswanath poosala , sridhar ramaswamy. venue: international conference on management of data. year: 1999