Cryptology ePrint Archive: BibTeX Citation of Report 2009/637

@misc{cryptoeprint:2009:637,
    author = {Xiao-shan Gao and Zhenyu Huang},
    title = {Efficient Characteristic Set Algorithms for Equation Solving in Finite Fields and Application in Analysis of Stream Ciphers},
    howpublished = {Cryptology ePrint Archive, Report 2009/637},
    year = {2009},
    note = {\url{http://eprint.iacr.org/}},
}

You will need the url.sty package (comes with most LaTeX installations) for the last line. Otherwise, remove the \url command.