Reference:

Javier Esparza, Andreas Gaiser, and Stefan Kiefer. A strongly polynomial algorithm for criticality of branching processes and consistency of stochastic context-free grammars. Inf. Process. Lett., 113(10-11):381–385, 2013.

Suggested BibTeX entry:

@article{DBLP:journalsiplEsparzaGK13,
    author = {Javier Esparza and Andreas Gaiser and Stefan Kiefer},
    journal = {Inf. Process. Lett.},
    number = {10-11},
    pages = {381-385},
    title = {A strongly polynomial algorithm for criticality of branching processes and consistency of stochastic context-free grammars},
    volume = {113},
    year = {2013}
}