“…so that the electromagnetic Faraday, F , and Maxwell, 4 * F , forms have a simple expression after introducing the Hodge duality ( * θ 2 = θ 3 ) in the space orthogonal to the Killing fields [10]. Taking into account Cartan's structure equations, expressing the torsionfree connection coefficients as one-forms, a, w, s, b and ν, (cfr.…”