Study of star-forming galaxies in SDSS up to redshift 0.4 - I. Metallicity evolution M. A. Lara-López, J. Cepa, A. Bongiovanni, A. M. Pérez García, H. Castañeda, M. Fernández Lorenzo, M. Pović and M. Sánchez-Portal A&A, 505 2 (2009) 529-539 Published online: 11 August 2009 DOI: 10.1051/0004-6361/200912214