title: query optimization in the presence of limited access patterns. authors: dan suciu , ioana manolescu , daniela florescu , alon y. levy. venue: sigmod conference. year: 1999
title: minimization of tree pattern queries. authors: sihem amer-yahia , sungran cho , laks v. s. lakshmanan , divesh srivastava. venue: international conference on management of data. year: 2001