Camille Salinesi Anne Etien Iyad Zoukar A Systematic Approach to Express IS Evolution Requirements Using Gap Modelling and Similarity Modelling Techniques. 338-352 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3084&spage=338 2004 conf/caise/2004 CAiSE db/conf/caise/caise2004.html#SalinesiEZ04