Mario Bravetti Roberto Gorrieri Roberto Lucchi Gianluigi Zavattaro Combining Partitions in SecSpaces. 31-47 2004 99 Electr. Notes Theor. Comput. Sci. http://dx.doi.org/10.1016/j.entcs.2004.02.002 db/journals/entcs/entcs99.html#BravettiGLZ04