Alfons Geser Dieter Hofbauer Johannes Waldmann Hans Zantema On Tree Automata that Certify Termination of Left-Linear Term Rewriting Systems. 353-367 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3467&spage=353 2005 conf/rta/2005 RTA db/conf/rta/rta2005.html#GeserHWZ05