@inproceedings{hepple-1990-normal,
    title = "Normal Form Theorem Proving for the {L}ambek Calculus",
    author = "Hepple, Mark",
    booktitle = "{COLING} 1990 Volume 2: Papers presented to the 13th International Conference on Computational Linguistics",
    year = "1990",
    url = "https://preview.aclanthology.org/fix-sig-urls/C90-2030/"
}