Adnan Vora Mikhail Nesterenko Sébastien Tixeuil Sylvie Delaët Universe Detectors for Sybil Defense in Ad Hoc Wireless Networks http://arxiv.org/abs/0805.0087 2008 CoRR abs/0805.0087 db/journals/corr/corr0805.html#abs-0805-0087 informal publication