Joseph Dunn Sean Davey Anne Descour Richard T. Snodgrass Sequenced Subset Operators: Definition and Implementation. 81-92 2002 conf/icde/2002 ICDE http://csdl.computer.org/comp/proceedings/icde/2002/1531/00/15310081abs.htm db/conf/icde/icde2002.html#DunnDDS02