**E** and **B**, then (29), (31) and (32) reproduce (13)-(18).

We have obtained two equivalent covariant versions of the electromagnetic field equations in the Minkowski spacetime. The first one is represented by equations (24) and (25) which are expressed in terms of the retarded four-potential defined in (23). The second one is represented by equations (29) and (31) which are expressed in terms of the retarded electromagnetic field (32) and its dual. This second version of the equations is identified with the covariant form of Maxwell’s equations. The basic physical ingredients of our axiomatic-heuristic procedure to find these equations were charge conservation mathematically represented by the covariant form of the continuity equation and a heuristic handling of this equation involving the retarded Green function of the wave equation.

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How should we interpret the procedure proposed here to *obtain* Maxwell’s equations? Have we really made a *derivation* of these equations or just a *construction* of them?

Following the traditional procedure starting with Maxwell’s equations, one introduces potentials and derives their wave equations (by adopting the Lorenz condition). By assuming appropriate boundary conditions the solutions of these wave equations yield the retarded potentials which are then differentiated to get the 