Potvliege, RM., Furtado, F., & Joachain, CJ. (1987). Multichannel Optical-model Theory of Proton Hydrogen and Proton Helium Elastic-scattering At Intermediate Energies. Journal of Physics B: Atomic, Molecular and Optical Physics, 20(8), 1771-1787. https://doi.org/10.1088/0022-3700/20/8/014 (Original work published 1987)