1. Dept. of Mathematical Sciences and Dept. of CIS, Bentley University and Bryant University, Waltham, MA and Smithfield, RI, USA
2. Dept. of Sociology, Université Dauphine, Paris, France
3. Dept. of Mathematical Sciences, SAMM and GREMAQ, Bentley University, Universités Paris 1 and Toulouse 1, Waltham, MA, USA, Paris and Toulouse, France
4. SAMM, Université Paris 1, Paris, France