Thierry Boy de la Tour Mnacho Echenim Overlapping Leaf Permutative Equations. 430-444 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3097&spage=430 2004 conf/cade/2004 IJCAR db/conf/cade/ijcar2004.html#TourE04