1. Department of Chemistry, Dainton Building, The University of Sheffield, Brook Hill, Sheffield, South Yorkshire S3 7HF, UK
2. Rohm and Haas France, European Laboratories, 371 rue L. van Beethoven, 06560 Sophia Antipolis, France
3. Rohm and Haas Company, Spring House Technical Center, P.O. Box 904, Spring House, Philadelphia, Pennsylvania 19477-0904