1. Kapteyn Astronomical Institute, University of Groningen, Postbus 800, NL-9700 AV Groningen, the Netherlands
2. INAF – Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze, Italy
3. Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands
4. Center for Theoretical Physics, Polish Academy of Sciences, al. Lotników 32/46, PL-02-668 Warsaw, Poland
5. INAF – Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli, Italy
6. Dipartimento di Scienze Fisiche, Università di Napoli Federico II, Compl. Univ. Monte S. Angelo, I-80126 Napoli, Italy
7. Argelander-Institut für Astronomie, Auf dem Hügel 71, D-53121 Bonn, Germany
8. Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
9. Shanghai Astronomical Observatory (SHAO), Nandan Road 80, Shanghai 200030, China