1. M. Ahlheim and B. Zysset, Sandoz Huningue, S. A. Avenue de Bale, F-68330 Huningue, France.
2. M. Barzoukas, A. Fort, C. Runser, Institute de Physique et Chemie des Materiaux de Strasbourg (UM 046 CNRS), 23 rue du Loess, F-67037 Strasbourg Cedex, France.
3. P. V. Bedworth and Z.-Y. Hu, Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA.
4. M. Blanchard-Desce, Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA, and Ecole Normale Supérieure, Département de Chimie (URA 1679 CNRS), 24 rue Lhomond 75231 Paris Cedex 05, France.
5. S. R. Marder and J. W. Perry, Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA, and Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
6. M. Staehelin, Sandoz Huningue, S. A. Avenue de Bale, F-68330 Huningue, France, and Institute of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland.