“…Thus, it is possible to use all the machinery of Lie group theory as it has been largely done for example with isometries in order to find, classify and study solutions of four-dimensional Einstein's field equations [51]. Similar analyses have been performed for conformal motions, affine collineations, linear collineations and conformal collineations (see [54,2,26,27,28,15,29,51] and references therein) with perhaps a less firmly established physical interpretation. An account of the classical symmetries studied in General Relativity can be found in [38,51].…”