Elisa Bertino Anna Cinzia Squicciarini A Flexible Access Control Model for Web Services. 13-16 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3055&spage=13 2004 conf/fqas/2004 FQAS db/conf/fqas/fqas2004.html#BertinoS04