1. Kapteyn Astronomical Institute, University of Groningen, Landleven 12, CH-9747 AD Groningen, The Netherlands
2. Astronomical Institute, Czech Academy of Sciences, Bŏcní II 1401, CZ-14131 Prague, Czech Republic
3. Columbia University, 550 W 120th St, New York, NY 10027, USA
4. Dunlap Institute for Astronomy and Astrophysics, 50 St George St, Toronto, ON M5S 3H4, Canada
5. Instituto de Física y Astronomía, Universidad de Valparaíso, Avda. Gran Bretaña 1111, Casilla 5030, Valparaíso, Chile
6. INAF, Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy