@article{crowdsourcingwithunsureoption,
  title = {Crowdsourcing with Unsure Option},
  author = {Yao-Xiang Ding and Zhi-Hua Zhou},
  year = {2016},
  eprint = {1609.00292},
  archivePrefix = {arXiv},
  url = {http://arxiv.org/abs/1609.00292v2},
}