The horizontal branch luminosity vs. metallicity in M 31 globular clusters L. Federici, C. Cacciari, M. Bellazzini, F. Fusi Pecci, S. Galleti and S. Perina A&A, 544 (2012) A155 Published online: 24 August 2012 DOI: 10.1051/0004-6361/201219317