Luo Xiao Dieter Wissmann Michael Brown Stefan Jablonski Hierarchical Concept Description and Learning for Information Extraction. 299-306 2001 conf/nlprs/2001 NLPRS http://www.afnlp.org/nlprs2001/pdf/0093-01.pdf db/conf/nlprs/nlprs2001.html#XiaoWBJ01