Hongrae Lee Raymond T. Ng Kyuseok Shim Extending Q-Grams to Estimate Selectivity of String Matching with Low Edit Distance. 195-206 2007 conf/vldb/2007 VLDB http://www.vldb.org/conf/2007/papers/research/p195-lee.pdf db/conf/vldb/vldb2007.html#LeeNS07