@article{Grigorchuk_1999,
    doi = {10.1016/s0304-3975(98)00161-3},
    url = {https://doi.org/10.1016%2Fs0304-3975%2898%2900161-3},
    year = {1999},
    month = {feb},
    publisher = {Elsevier {BV}},
    volume = {215},
    number = {1-2},
    pages = {325--327},
    author = {R.I. Grigorchuk and A. Mach{\'{\i}}},
    title = {An example of an indexed language of intermediate growth},
    journal = {Theoretical Computer Science}
}

@article{Grigorchuk_1999, doi = {10.1016/s0304-3975(98)00161-3}, url = {https://doi.org/10.1016%2Fs0304-3975%2898%2900161-3}, year = {1999}, month = {feb}, publisher = {Elsevier {BV}}, volume = {215}, number = {1-2}, pages = {325--327}, author = {R.I. Grigorchuk and A. Mach{\'{\i}}}, title = {An example of an indexed language of intermediate growth}, journal = {Theoretical Computer Science} }