F. Surot (1, 4), E. Valenti (1), S. L. Hidalgo (2, 3), M. Zoccali (4, 5), E. Sökmen (2, 3), M. Rejkuba (1, 6), D. Minniti (5, 7, 8), O. A. Gonzalez (9), S. Cassisi (10, 11), A. Renzini (12), A. Weiss (13) ((1) European Southern Observatory, (2) Instituto de Astrofísica de Canarias, (3) Department of Astrophysics University of La Laguna, (4) Instituto de Astrofísica Pontificia Universidad Católica de Chile, (5) Millennium Institute of Astrophysics, (6) Excellence Cluster Universe, (7) Departamento de Ciencias Físicas Universidad Andrés Bello, (8) Vatican Observatory, (9) Institute for Astronomy University of Edinburgh, (10) INAF - Astronomical Observatory of Abruzzo, (11) INFN, (12) INAF - Osservatorio Astronomico di Padova, (13) Max-Planck-Institut für Astrophysik)
