Javier Esparza Antonín Kucera Richard Mayr Model Checking Probabilistic Pushdown Automata. 12-21 2004 conf/lics/2004 LICS http://csdl.computer.org/comp/proceedings/lics/2004/2192/00/21920012abs.htm db/conf/lics/lics2004.html#EsparzaKM04