1. Institut Jean Lamour (UMR7198 CNRS, Université de Lorraine), Parc de Saurupt, 54011 Nancy Cedex, France
2. Department
of Mathematics and Physics, Lappeenranta University of Technology, P.O. Box 20, FIN-53851 Lappeenranta, Finland
3. Mines
Nancy, Université de Lorraine, 54042 Nancy, France
4. Department
of Earth and Environmental Sciences, Crystallography Section, Ludwig-Maximilians-Universität München, Theresienstr. 41, D-80333 München, Germany