Fernández-Rañada, Antonio2023-06-212023-06-211974-07-150556-282110.1103/PhysRevD.10.517https://hdl.handle.net/20.500.14352/64914© 1974 The American Physical Society. We wish to express our appreciation to Dr. B. Carreras for carefully reading our manuscript and for very useful discussions and suggestions during the completion of this paper.The classical electromagnetic interactions of a nonlinear spinor field are studied in perturbation theory. When Pauli terms are included, the model describes with reasonable accuracy (within the assumed approximations) such properties of the nucleons as spin, charge, magnetic moment, and the proton mass. With no other information one can calculate the proton-neutron mass difference, which comes out of the wrong sign and of the same size as in quantum electrodynamics.engjournal articlehttp://dx.doi.org/10.1103/PhysRevD.10.517http://journals.aps.orgopen access537ElectricidadElectrónica (Física)2202.03 Electricidad