First Author:   Thi hong hanh Pham University of Rouen hanh.phamhong@gmail.com   University of Rouen, 3, avenue Pasteur Rouen, Cedex 1, F-76186, France   +33(0)2 32 76 96 56(Phone) +33(0)2 32 76 96 56(Fax) Second Author: Duc thinh Nguyen Ministry of Planning and Investment of Vietnam hnihtcud@yahoo.com   Hanoi, Vietnam