José Meseguer Miguel Palomino Narciso Martí-Oliet 2-16 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2741&spage=2 2003 conf/cade/2003 CADE db/conf/cade/cade2003.html#MeseguerPM03