@article{Baron_1981,
    doi = {10.1016/s0019-9958(81)90634-3},
    url = {https://doi.org/10.1016%2Fs0019-9958%2881%2990634-3},
    year = {1981},
    month = {feb},
    publisher = {Elsevier {BV}},
    volume = {48},
    number = {2},
    pages = {109--118},
    author = {Gerd Baron and Werner Kuich},
    title = {The characterization of nonexpansive grammars by rational power series},
    journal = {Information and Control}
}

@article{Baron_1981, doi = {10.1016/s0019-9958(81)90634-3}, url = {https://doi.org/10.1016%2Fs0019-9958%2881%2990634-3}, year = {1981}, month = {feb}, publisher = {Elsevier {BV}}, volume = {48}, number = {2}, pages = {109--118}, author = {Gerd Baron and Werner Kuich}, title = {The characterization of nonexpansive grammars by rational power series}, journal = {Information and Control} }