Reference:

Javier Esparza, Antonín Kučera, and Richard Mayr. Model checking probabilistic pushdown automata. In LICS 2004. IEEE Computer Society, 2004.

Suggested BibTeX entry:

@inproceedings{EKM04,
    author = {Javier Esparza and Anton\'{\i}n Ku\v{c}era and Richard Mayr},
    booktitle = {LICS 2004},
    publisher = {IEEE Computer Society},
    title = {Model Checking Probabilistic Pushdown Automata},
    year = {2004}
}