The mass of the neutrino
F C Frank · Proceedings of the Physical Society · 1947
From a collation of the energies involved in nuclear reactions and radioactive decays, which together represent closed cycles, it is shown that the rest-mass of the neutrino, m v , is beyond any reasonable doubt less than that of the electron, m e , and probably less than m e /10. It cannot be shown with certainty to be measurably distinct from zero.