@inproceedings{zhu-etal-2019-learning,
    title = "Learning to Ask Unanswerable Questions for Machine Reading Comprehension",
    author = "Zhu, Haichao  and
      Dong, Li  and
      Wei, Furu  and
      Wang, Wenhui  and
      Qin, Bing  and
      Liu, Ting",
    editor = "Korhonen, Anna  and
      Traum, David  and
      M{\`a}rquez, Llu{\'i}s",
    booktitle = "Proceedings of the 57th Annual Meeting of the Association for Computational Linguistics",
    month = jul,
    year = "2019",
    address = "Florence, Italy",
    publisher = "Association for Computational Linguistics",
    url = "https://preview.aclanthology.org/fix-sig-urls/P19-1415/",
    doi = "10.18653/v1/P19-1415",
    pages = "4238--4248"
}