. . "Spacetime symmetries" . . "Symmetries in General Relativity" . . "4-dimensional spacetimes" . . . "space-time symmetry" . "spacetime symmetries" . "symmetries" . "symmetry" . "spacetime symmetry" . . . "symmetry group" . "Spacetime symmetries" . "symmetries in general relativity" . "symmetries of space and time" .