title: re-tree : an efficient index structure for regular expressions. authors: chee yong chan , minos n. garofalakis , rajeev rastogi. venue: vldb j.. year: 2003
title: the a-tree : an index structure for high-dimensional spaces using relative approximation. authors: yasushi sakurai , masatoshi yoshikawa , shunsuke uemura , haruhiko kojima. venue: very large data bases. year: 2000