Riccardo Focardi Sabina Rossi Information flow security in dynamic contexts. 65-110 2006 14 Journal of Computer Security 1 http://iospress.metapress.com/openurl.asp?genre=article&issn=0926-227X&volume=14&issue=1&spage=65 db/journals/jcs/jcs14.html#FocardiR06