Clemens Grabmayer Jan Willem Klop Bas Luttik Reflections on a Geometry of Processes. 183-190 2006 162 Electr. Notes Theor. Comput. Sci. http://dx.doi.org/10.1016/j.entcs.2005.12.111 db/journals/entcs/entcs162.html#GrabmayerKL06