Odinaldo Rodrigues Artur S. d'Avila Garcez Alessandra Russo Reasoning About Requirements Evolution Using Clustered Belief Revision. 41-51 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3171&spage=41 2004 conf/sbia/2004 SBIA db/conf/sbia/sbia2004.html#RodriguesGR04