James P. Delgrande Abhaya C. Nayak Maurice Pagnucco Prolegomenon to a Theory of Conservative Belief Revision. 1391-1393 2003 conf/ijcai/2003 IJCAI db/conf/ijcai/ijcai2003.html#DelgrandeNP03 http://ijcai.org/Proceedings/03/Papers/212.pdf