@misc{cryptoeprint:2004:250,
    author = {Jing Xu and Zhenfeng Zhang and Dengguo Feng},
    title = {Identity Based Threshold Proxy Signature},
    howpublished = {Cryptology ePrint Archive, Report 2004/250},
    year = {2004},
    url = {http://eprint.iacr.org/2004/250},
}