Central enhancement of the nitrogen-to-oxygen abundance ratio in barred galaxies E. Florido, A. Zurita, I. Pérez, E. Pérez-Montero, P. R. T. Coelho and D. A. Gadotti A&A, 584 (2015) A88 Published online: 08 December 2015 DOI: 10.1051/0004-6361/201526191