1. L.I.B., University of Burgundy, B.P. 47870, 21078 Dijon Cedex, France
2. I.U.T. of Dijon, University of Burgundy-Franche-Comté, B.P. 47870, 21078 Dijon Cedex, France
3. U.P.H.F. - Campus Mont Houy - 59313 Valenciennes Cedex 9, France
4. X.L.I.M., U.M.R. 7252, University of Poitiers, France
5. Laboratoire IRIT, U.M.R. 5505, University Paul Sabatier, 31 000 Toulouse, France