Ricardo Lopes Vítor Santos Costa Fernando M. A. Silva Pruning in the Extended Andorra Model. 120-134 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3057&spage=120 2004 conf/padl/2004 PADL db/conf/padl/padl2004.html#LopesCS04