J.P. Egger, R. Corfu, P. Gretillat, C. Lunke, J. Piffaretti, et al.. Comparison of $\pi^+$ and $\pi^-$ elastic scattering off $^{40}$Ca and $^{48}$Ca showing the possibility to extract a neutron radius for $^{48}$Ca.
Swiss Physical Society Autumn Meeting, Oct 1977, Berne, Switzerland. pp.85-86.
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