@article{180405938,
  title = {Unbiased Learning to Rank with Unbiased Propensity Estimation},
  author = {Qingyao Ai and Keping Bi and Cheng Luo and Jiafeng Guo and W. Bruce Croft},
  year = {2018},
  eprint = {1804.05938},
  archivePrefix = {arXiv},
  url = {http://arxiv.org/abs/1804.05938v2},
}