1. Statistics Section, Department of Mathematics, Imperial College London, London SW7 2AZ, UK
2. Center for Space and Atmospheric Research, Embry-Riddle Aeronautical University, Daytona Beach, USA
3. Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany
4. Argiope Technical Solutions, Florida, USA
5. Institut d'astrophysique de Paris, Paris, France