Four-dimensional aether-like Lorentz-breaking QED revisited and problem of ambiguities A. P. Baeta Scarpelli, T. Mariz, J. R. Nascimento and A. Yu. Petrov Eur. Phys. J. C, 73 8 (2013) 2526 Published online: 21 August 2013 DOI: 10.1140/epjc/s10052-013-2526-3