@inproceedings{liu-etal-2013-question,
    title = "Question Difficulty Estimation in Community Question Answering Services",
    author = "Liu, Jing  and
      Wang, Quan  and
      Lin, Chin-Yew  and
      Hon, Hsiao-Wuen",
    editor = "Yarowsky, David  and
      Baldwin, Timothy  and
      Korhonen, Anna  and
      Livescu, Karen  and
      Bethard, Steven",
    booktitle = "Proceedings of the 2013 Conference on Empirical Methods in Natural Language Processing",
    month = oct,
    year = "2013",
    address = "Seattle, Washington, USA",
    publisher = "Association for Computational Linguistics",
    url = "https://preview.aclanthology.org/fix-sig-urls/D13-1009/",
    pages = "85--90"
}