@inproceedings{SIGIR-2009-WangZ,
	author        = "Jun Wang and Jianhan Zhu",
	booktitle     = "{Proceedings of the 32nd International ACM SIGIR Conference on Research and Development in Information Retrieval}",
	doi           = "10.1145/1571941.1571963",
	isbn          = "978-1-60558-483-6",
	pages         = "115--122",
	publisher     = "{ACM}",
	title         = "{Portfolio theory of information retrieval}",
	year          = 2009,
}