1. R. Bingham, B. J. Kellett, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, UK.
2. J. M. Dawson, Department of Physics, University of California, Los Angeles, CA 90024, USA.
3. V. D. Shapiro, Department of Physics, University of California at San Diego, La Jolla, CA 92092, USA.
4. D. A. Mendis, Department of Electrical and Computing Science, University of California at San Diego, La Jolla, CA 92092, USA.