2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/85573The expression for the Coulomb-gauge vector potential in terms of the `instantaneous' magnetic field derived by Stewart [2003 Eur. J. Phys. 24, 519] by employing Jefimenko's equation for the magnetic field and Jackson's formula for the Coulomb-gauge vector potential can be proven much more simply.REVTeX, 3 pages. The same version as that which will appear in European Journal of PhysicsClassical PhysicsGeneral Physicstext