1. R. J. Kelley, C. Quitmann, M. Onellion, Applied Superconductivity Center, University of Wisconsin, Madison, WI 53706, USA.
2. H. Berger, P. Almeras, G. Margaritondo, Institut de Physique Appliquée, École Polytechnique Fédérale, CH-1015 Lausanne, Switzerland.