A. Cordier, B. Delcourt, P. Eschstruth, F. Fulda, G. Grosdidier, et al.. Cross section of the reaction $e^+e^- \rightarrow \pi^+\pi^-\pi^+\pi^-$ for center of mass energies from 890 to 1100 MeV.
Physics Letters B, Elsevier, 1979, 81, pp.389-392.
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