Pierangelo Dell'Acqua Luís Moniz Pereira Preferring and Updating in Abductive Multi-agent Systems. 57-73 2001 conf/esaw/2001 ESAW http://link.springer.de/link/service/series/0558/bibs/2203/22030057.htm db/conf/esaw/esaw2001.html#DellAcquaP01