Reference:

Javier Esparza, Antonín Kučera, and Richard Mayr. Quantitative analysis of probabilistic pushdown automata: Expectations and variances. Technical Report FIMU-RS-2005-07, Masaryk University, 2005.

Suggested BibTeX entry:

@techreport{EKM05rep,
    author = {Javier Esparza and Anton\'{\i}n Ku\v{c}era and Richard Mayr},
    institution = {Masaryk University},
    number = {FIMU-RS-2005-07},
    title = {Quantitative Analysis of Probabilistic Pushdown Automata: Expectations and Variances},
    year = {2005}
}