E. Eichten; K. Gottfried; T. Kinoshita; J. Kogut; K. D. Lane; T.-M. Yan (1975). "Spectrum of Charmed Quark-Antiquark Bound States". Physical Review Letters. 34 (6): 369–372. Bibcode:1975PhRvL..34..369E. doi:10.1103/PhysRevLett.34.369.
E. Eichten; K. Gottfried; T. Kinoshita; J. Kogut; K. D. Lane; T.-M. Yan (1975). "Spectrum of Charmed Quark-Antiquark Bound States". Physical Review Letters. 34 (6): 369–372. Bibcode:1975PhRvL..34..369E. doi:10.1103/PhysRevLett.34.369.