Parosh Aziz Abdulla Ahmed Bouajjani Lukás Holík Lisa Kaati Tomás Vojnar Composed Bisimulation for Tree Automata. 685-700 2009 20 Int. J. Found. Comput. Sci. 4 http://dx.doi.org/10.1142/S0129054109006814 db/journals/ijfcs/ijfcs20.html#AbdullaBHKV09