Observation of the narrow state X(3872) → J/ψπ+π- in p̄p collisions at √s = 1.96 TeV - Acosta, D; Affolder, T; Ahn, M; Akimoto, T; Albrow, MG; Ambrose, D; Amerio, S; Amidei, D; Anastassov, A; Anikeev, K; Annovi, A; Antos, J; et al. (Physical Review Letters, 2004)