Observation ofJ/ψ-pair production in pp collisions ats=7TeV - Aaij, R; Adeva, B; Adinolfi, M; Adrover, C; Affolder, A; Ajaltouni, Z; Albrecht, J; Alessio, F; Alexander, M; Alkhazov, G; Alvarez, Cartelle P; Alves, AA; et al. (Physics Letters B, 2012)