1. M. Lutz et al. (PANDA Collaboration), (2009), arXiv:0903.3905 [hep-ex].
2. Proton–antiproton annihilation into massive leptons and polarization phenomena
3. Determination of the electric and magnetic form factors of the proton in the time-like region
4. J. Lees et al., “Measurement of the e+ + e− → p+p¯ cross section in the energy range from 3.0 to 6.5 GeV,” Tech. Rep. (BaBar, 2013).
5. M. Ablikim et al., Phys.Rev. D 91 (2015).