1. National Institute for Physics and Nuclear Engineering, P. O. Box MG-6, Bucharest, Romania
2. Institut fur Kernphysik, J. W. Goethe Universitet, August Euler Strasse 6, Frankfurt am Main, Germany
3. Kernfysisch Versneller Instituut, Zernikelaan 25, 9747 AA Groningen, The Netherlands
4. Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Via S. Sofia 44, 95123 Catania, Italy