First Author:   Thanh tam Nguyen Huu CREAM & Economics Department, University of Rouen nguyentam9483@gmail.com   3 avenue Pasteur Rouen cedex 1, 76186, France   +33 (0)2 32 76 98 72(Phone) +33 (0)2 32 76 98 72(Fax) https://sites.google.com/site/huuthanhtamnguyenwebsite/