1. Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156,
38042 Grenoble Cedex 9, France
2. Department of Physical Chemistry, Lund University, P.O. Box 124, S-221 00 Lund, Sweden
3. Department of Chemistry, Durham University, South Road, DH1 3LE United Kingdom
4. Institute of Chemistry, Eötvös Loránd University, Budapest
112, P.O. Box 32, H-1518 Hungary