@inproceedings{gao2011clickthrough,
  title={Clickthrough-based latent semantic models for web search},
  author={Gao, Jianfeng and Toutanova, Kristina and Yih, Wen-tau},
  booktitle={Proceedings of the 34th international ACM SIGIR conference on Research and development in Information Retrieval},
  pages={675--684},
  year={2011},
  organization={ACM}
}