Homogeneous metallicities and radial velocities for Galactic globular clusters - First CaT metallicities for twenty clustersI. Saviane, G. S. Da Costa, E. V. Held, V. Sommariva, M. Gullieuszik, B. Barbuy and S. OrtolaniA&A, 540 (2012) A27DOI: https://doi.org/10.1051/0004-6361/201118138