1. Istituto Nazionale di Astrofisica, Osservatorio Astrofisico di Torino, Via Osservatorio 20, I-10024 Pino Torinese (TO), Italy
2. Departamento de Astronomía, Universidad de Guanajuato, Callejón de Jalisco S/N, 36023 Guanajuato, GTO, Mexico
3. Sterrewacht Leiden, University of Leiden, PO Box 9513, NL-2300 RA, Leiden, the Netherlands
4. Zentrum für Astronomie (Center for Astronomy), Heidelberg University, Mönchhofstr 14, D-69120 Heidelberg, Germany