[1] U.M.R CNRS 8524,
[2] Laboratoire Paul Painleve,undefined
[3] Bat.M2,undefined
[4] Universite Lille 1,undefined
[5] 59 655 Villeneuve d’Ascq Cedex and U.M.R CNRS 8020 CLAREE,undefined
[6] IAE de Lille 104,undefined
[7] Avenue du Peuple Belge,undefined
[8] 59043 Lille Cedex,undefined
[9] Department of Statistics and Probability,undefined
[10] A-413 Wells Hall,undefined
[11] Michigan State University,undefined
[12] East Lansing,undefined
[13] MI 48823,undefined