title: the x-tree : an index structure for high-dimensional data 1996. authors: hans-peter kriegel , stefan berchtold , daniel a. keim. venue: vldb. year: nan
title: the a-tree : an index structure for high-dimensional spaces using relative approximation yasushi sakurai , masatoshi yoshikawa , shunsuke uemura , haruhiko kojima. authors: nan. venue: very large data bases. year: 2000.0