Andrea Bondavalli Enrico De Giudici Stefano Porcarelli Salvatore Sabina Fabrizio Zanini A Freshness Detection Mechanism for Railway Applications. 292-301 2004 conf/prdc/2004 PRDC http://doi.ieeecomputersociety.org/10.1109/PRDC.2004.1276579 db/conf/prdc/prdc2004.html#BondavalliGPSZ04