@TechReport{YthiWalkBier12,
author = {Jeanne Ythier and Joan Walker and Michel Bierlaire },
title = {The role of the social network and the usage of communication in travel behavior measured with Smartphone data},
institution = {Transport and Mobility Laboratory, Ecole Polytechnique F\'ed\'erale de Lausanne},
number = {TRANSP-OR 120801},
year = {2012}
}