Daniele Gorla Matthew Hennessy Vladimiro Sassone Security Policies as Membranes in Systems for Global Computing. 23-42 2005 138 Electr. Notes Theor. Comput. Sci. 1 http://dx.doi.org/10.1016/j.entcs.2005.05.003 db/journals/entcs/entcs138.html#GorlaHS05