“…Comparing the first Equation (2) and Equation (17), it follows that for the Lorentz force the corresponding scalar χ vanishes identically. Then, supposing that the Lorentz force is the only force acting on a charged particle in the electromagnetic field, Equation (20) implies that m is constant, consistent with Planck's assumption tacitly made in [3]. As another example, consider a three-force f = −(g/γ u )∇Φ, where a Lorentz scalar g plays the same role as does charge in electromagnetism, and Φ = Φ(r, t) is a Lorentz scalar field; f represents the relativistic force arising in the scalar meson theory of the nucleus [10,[12][13][14].…”