1. Department of Astronomy, University of Texas at Austin, Austin, TX 78712-1083, USA
2. Observatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS UMR 7550, 11 rue de l’Université, F-67000 Strasbourg, France
3. Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
4. Astronomy Center, Department of Physics & Astronomy, Pevensey II Building, University of Sussex, Falmer, Brighton BN1 9QH, UK
5. Institute for Theoretical Physics, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
6. Departamento de Física Teórica and CIAFF, Módulo 15 Universidad Autónoma de Madrid, E-28049, Madrid, Spain
7. Leibniz-Institute für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany
8. Department of Physics & Astronomy, University of California, Riverside, CA 92521, USA
9. Korea Astronomy and Space Science Institute, Daejeon, 305-348, Korea
10. Racah Institute of Physics, Hebrew University, Jerusalem 91904, Israel