2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/130072This paper was withdrawn by the editors of SIGMA as it essentially coincides with Phys. Lett. B 451 (1999), no. 3-4, 349-353.The paper withdrawn by the editors of SIGMA (Symmetry, Integrability and Geometry: Methods and Applications)High Energy Physics - TheoryMathematical Physicstext