@article{Greibach_1973,
    doi = {10.1137/0202025},
    url = {https://doi.org/10.1137%2F0202025},
    year = {1973},
    month = {dec},
    publisher = {Society for Industrial {\&} Applied Mathematics ({SIAM})},
    volume = {2},
    number = {4},
    pages = {304--310},
    author = {Sheila A. Greibach},
    title = {The Hardest Context-Free Language},
    journal = {{SIAM} Journal on Computing}
}

@article{Greibach_1973, doi = {10.1137/0202025}, url = {https://doi.org/10.1137%2F0202025}, year = {1973}, month = {dec}, publisher = {Society for Industrial {\&} Applied Mathematics ({SIAM})}, volume = {2}, number = {4}, pages = {304--310}, author = {Sheila A. Greibach}, title = {The Hardest Context-Free Language}, journal = {{SIAM} Journal on Computing} }