@article{Greibach:JACM:1965,
    doi = {10.1145/321250.321254},
    url = {https://doi.org/10.1145%2F321250.321254},
    year = {1965},
    month = {jan},
    publisher = {Association for Computing Machinery ({ACM})},
    volume = {12},
    number = {1},
    pages = {42--52},
    author = {Sheila A. Greibach},
    title = {A New Normal-Form Theorem for Context-Free Phrase Structure Grammars},
    journal = {Journal of the {ACM}}
}

@article{Greibach:JACM:1965, doi = {10.1145/321250.321254}, url = {https://doi.org/10.1145%2F321250.321254}, year = {1965}, month = {jan}, publisher = {Association for Computing Machinery ({ACM})}, volume = {12}, number = {1}, pages = {42--52}, author = {Sheila A. Greibach}, title = {A New Normal-Form Theorem for Context-Free Phrase Structure Grammars}, journal = {Journal of the {ACM}} }