Alain Barrat Ciro Cattuto Vittoria Colizza Jean-Francois Pinton Wouter Van den Broeck Alessandro Vespignani High resolution dynamical mapping of social interactions with active RFID http://arxiv.org/abs/0811.4170 2008 CoRR abs/0811.4170 db/journals/corr/corr0811.html#abs-0811-4170 informal publication