@ARTICLE{6095524, author={Wang, Cong and Cao, Ning and Ren, Kui and Lou, Wenjing}, journal={IEEE Transactions on Parallel and Distributed Systems}, title={Enabling Secure and Efficient Ranked Keyword Search over Outsourced Cloud Data}, year={2012}, volume={23}, number={8}, pages={1467-1479}, doi={10.1109/TPDS.2011.282}}