Eugene Asarin Gordon J. Pace Gerardo Schneider Sergio Yovine Algorithmic analysis of polygonal hybrid systems, Part II: Phase portrait and tools. 1-26 2008 390 Theor. Comput. Sci. 1 http://dx.doi.org/10.1016/j.tcs.2007.09.025 db/journals/tcs/tcs390.html#AsarinPSY08