Using classical Cepheids to study the far side of the Milky Way disk - I. Spectroscopic classification and the metallicity gradient
J. H. Minniti, L. Sbordone, A. Rojas-Arriagada, M. Zoccali, R. Contreras Ramos, D. Minniti, M. Marconi, V. F. Braga, M. Catelan, S. Duffau, W. Gieren and A. A. R. Valcarce
