Gauge invariance and the CPT and Lorentz violating induced Chern–Simons-like term in extended QED A. P. Baêta Scarpelli, Marcos Sampaio, M. C. Nemes and B. Hiller Eur. Phys. J. C, 56 4 (2008) 571-578 Published online: 29 July 2008 DOI: 10.1140/epjc/s10052-008-0677-4