@inproceedings{campbell-2004-using,
    title = "Using Linguistic Principles to Recover Empty Categories",
    author = "Campbell, Richard",
    booktitle = "Proceedings of the 42nd Annual Meeting of the Association for Computational Linguistics ({ACL}-04)",
    month = jul,
    year = "2004",
    address = "Barcelona, Spain",
    url = "https://preview.aclanthology.org/fix-sig-urls/P04-1082/",
    doi = "10.3115/1218955.1219037",
    pages = "645--652"
}