@article{Choffrut_2007,
    doi = {10.1016/j.tcs.2007.04.003},
    url = {https://doi.org/10.1016%2Fj.tcs.2007.04.003},
    year = {2007},
    month = {aug},
    publisher = {Elsevier {BV}},
    volume = {381},
    number = {1-3},
    pages = {274--279},
    author = {Christian Choffrut and Flavio D'Alessandro and Stefano Varricchio},
    title = {On the separability of sparse context-free languages and of bounded rational relations},
    journal = {Theoretical Computer Science}
}

@article{Choffrut_2007, doi = {10.1016/j.tcs.2007.04.003}, url = {https://doi.org/10.1016%2Fj.tcs.2007.04.003}, year = {2007}, month = {aug}, publisher = {Elsevier {BV}}, volume = {381}, number = {1-3}, pages = {274--279}, author = {Christian Choffrut and Flavio D'Alessandro and Stefano Varricchio}, title = {On the separability of sparse context-free languages and of bounded rational relations}, journal = {Theoretical Computer Science} }