@inproceedings{CIKM-2007-WangFZ,
	author        = "Xuanhui Wang and Hui Fang and ChengXiang Zhai",
	booktitle     = "{Proceedings of the 16th ACM International Conference on Information and Knowledge Management}",
	doi           = "10.1145/1321440.1321593",
	isbn          = "978-1-59593-803-9",
	pages         = "991--994",
	publisher     = "{ACM}",
	title         = "{Improve retrieval accuracy for difficult queries using negative feedback}",
	year          = 2007,
}