Kewei Tu Jing Lu Haiping Zhu Guowei Liu Yong Yu A Semantic Search Approach by Graph Matching with Negations and Inferences. 378-391 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2746&spage=378 2003 conf/iccs/2003 ICCS db/conf/iccs/iccs2003.html#TuLZLY03