Salvatore La Torre Aniello Murano Margherita Napoli Weak Muller Acceptance Conditions for Tree Automata. 240-254 2002 conf/vmcai/2002 VMCAI http://dx.doi.org/10.1007/3-540-47813-2_17 db/conf/vmcai/vmcai2002.html#TorreMN02