Mohamed Shehab Elisa Bertino Arif Ghafoor Proactive Role Discovery in Mediator-Free Environments. 150-159 2008 Peer-to-Peer Computing http://doi.ieeecomputersociety.org/10.1109/P2P.2008.52 conf/p2p/2008 db/conf/p2p/p2p2008.html#ShehabBG08