Ivan Djordjevic Theodosis Dimitrakos Towards Dynamic Security Perimeters for Virtual Collaborative Networks. 191-205 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2995&spage=191 2004 conf/itrust/2004 iTrust db/conf/itrust/itrust2004.html#DjordjevicD04