Dimitrios Mavroeidis Peter A. Flach Improved Distances for Structured Data. 251-268 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2835&spage=251 2003 conf/ilp/2003 ILP db/conf/ilp/ilp2003.html#MavroeidisF03