Guimei Liu Hongjun Lu Yabo Xu Jeffrey Xu Yu Ascending Frequency Ordered Prefix-tree: Efficient Mining of Frequent Patterns. 65-72 2003 conf/dasfaa/2003 DASFAA http://computer.org/proceedings/dasfaa/1895/18950065abs.htm db/conf/dasfaa/dasfaa2003.html#LiuLXY03