Constraints on Sub-GeV Dark-Matter-Electron Scattering from the DarkSide-50 Experiment. - Agnes P; Albuquerque IFM; Alexander T; Alton AK; Araujo GR; Asner DM; Ave M; Back HO; Baldin B; Batignani G; Biery K; Bocci V; et al. (Physical review letters, 2018)