Non-minimal coupling to a Lorentz-violating background and topological implications H. Belich, T. Costa-Soares, M. M. FerreiraJr. and J. A. Helayël-Neto Eur. Phys. J. C, 41 3 (2005) 421-426 Published online: 15 June 2005 DOI: 10.1140/epjc/s2005-02240-y