Measuring propagation speed of Coulomb fields R. de Sangro, G. Finocchiaro, P. Patteri, M. Piccolo and G. Pizzella Eur. Phys. J. C, 75 3 (2015) 137 Published online: 24 March 2015 DOI: 10.1140/epjc/s10052-015-3355-3