Radiative events as a probe of dark forces at GeV-scale e + e − collidersL. Barzè, G. Balossini, C. Bignamini, C.M. Carloni Calame, G. Montagna, O. Nicrosini and F. PiccininiEur. Phys. J. C, 71 6 (2011) 1680DOI: https://doi.org/10.1140/epjc/s10052-011-1680-8