Reference:

Javier Esparza, Pierre Ganty, Stefan Kiefer, and Michael Luttenberger. Parikh's theorem: A simple and direct construction. CoRR, abs/1006.3825, 2010.

Suggested BibTeX entry:

@article{EGKL10:parikh,
    author = {Javier Esparza and Pierre Ganty and Stefan Kiefer and Michael Luttenberger},
    journal = {CoRR},
    title = {Parikh's Theorem: A simple and direct construction},
    volume = {abs/1006.3825},
    year = {2010}
}