Jon Iturrioz Oscar Díaz Sergio Fernández Anzuola Facing Document-Provider Heterogeneity in Knowledge Portals. 384-397 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3084&spage=384 2004 conf/caise/2004 CAiSE db/conf/caise/caise2004.html#IturriozDA04