Weining Qian Long Zhang Yuqi Liang Hailei Qian Wen Jin A Two-Level Method for Clustering DTDs. 41-52 http://link.springer.de/link/service/series/0558/bibs/1846/18460041.htm 2000 conf/waim/2000 Web-Age Information Management db/conf/waim/waim2000.html#QianZLQJ00