L. Maiani, F. Piccinini, V. Riquer and A.D. Polosa (2005). "Diquark-antidiquarks with hidden or open charm and the nature of X(3872)". Physical Review D71: 014028. doi:10.1103/PhysRevD.71.014028. Bibcode: 2005PhRvD..71a4028M.
A. Ali, C. Hambrock, M.J. Aslam; Hambrock; Aslam (2010). "Tetraquark Interpretation of the BELLE Data on the Anomalous Υ(1S)π+π- and Υ(2S)π+π- Production near the Υ(5S) Resonance". Physical Review Letters104 (16): 162001. doi:10.1103/PhysRevLett.104.162001. Bibcode: 2010PhRvL.104p2001A.
L. Maiani, F. Piccinini, V. Riquer and A.D. Polosa (2005). "Diquark-antidiquarks with hidden or open charm and the nature of X(3872)". Physical Review D71: 014028. doi:10.1103/PhysRevD.71.014028. Bibcode: 2005PhRvD..71a4028M.
A. Ali, C. Hambrock, M.J. Aslam; Hambrock; Aslam (2010). "Tetraquark Interpretation of the BELLE Data on the Anomalous Υ(1S)π+π- and Υ(2S)π+π- Production near the Υ(5S) Resonance". Physical Review Letters104 (16): 162001. doi:10.1103/PhysRevLett.104.162001. Bibcode: 2010PhRvL.104p2001A.