2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/95854Editorial note: In this lecture, held at the meeting of the Berlin Physical Society, October 25, 1929, Lanczos discusses a nonlinear generalization of Proca's equation (derived from his ``fundamental equation'') such that the mass is multiplied by a scalar field function.20 pages. 4 figures. Initial translation by Josef Illy and Judith Konstag Masko. Final translation and editorial notes by Andre GsponerHistory and Philosophy of Physicstext