Salvatore La Torre Aniello Murano Margherita Napoli Weak Muller acceptance conditions for tree automata. 233-250 2005 332 Theor. Comput. Sci. 1-3 http://dx.doi.org/10.1016/j.tcs.2004.10.027 db/journals/tcs/tcs332.html#TorreMN05