1. Astronomický ústav, Akademie věd České republiky, Fričova 298, CZ-251 65 Ondřejov, Czech Republic
2. Tartu Observatory, University of Tartu, 61602 Tõravere, Tartumaa, Estonia
3. IESL, Foundation for Research and Technology-Hellas, 100 Nikolaou Plastira Street, 71110 Heraklion, Crete, Greece
4. Department of Physics, University of Crete, P.O. Box 2208, 71003 Heraklion, Crete, Greece
5. Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium
6. Special Astrophysical Observatory of the Russian Academy of Sciences, Nizhnii Arkhyz 369167, Russia