Ninghui Li William H. Winsborough John C. Mitchell Beyond Proof-of-Compliance: Safety and Availability Analysis in Trust Management. 123-139 2003 conf/sp/2003 IEEE Symposium on Security and Privacy http://csdl.computer.org/comp/proceedings/sp/2003/1940/00/19400123abs.htm db/conf/sp/sp2003.html#LiWM03