1. Augustin J E, Cosme G, Couchot F, et al. Study of the J/ψ decay into five pions. Nucl Phys B, 1989, 320: 1–19
2. Wu N. Search for σ particle in J/ψ to ωππ. In: Proceedings of the XXXVIth Rencontres de Moriond. Les Arcs: Moriond Workshop, 2001, 3: 17–24
3. Alde D, Bellazzini R, Binon F G, et al. Study of the π 0 π 0 system in pp central collisions at 450 GeV/c. Phys Lett B, 1997, 397: 350–356
4. Ishida T. The σ particle. In: Proceedings of International Conference on Hadron Spectroscopy. Manchester: World Scientific, 1995
5. Markushin V E, Locher M P. Structure of the light scalar mesons from a coupled channel analysis of the S wave ππ − KK − scattering. Frascati Phys Ser, 1999, 15: 229–236