Daniel R. Brooks Esra Erdem James W. Minett Donald Ringe Character-Based Cladistics and Answer Set Programming. 37-51 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3350&spage=37 2005 conf/padl/2005 PADL db/conf/padl/padl2005.html#BrooksEMR05