equation icon  [ a a2 c d 3] gtt = - 1 + 2aa ^y + (aay^ ) + R0c0d^y ^y + O(s ) , (129) 2- c d 3 gta = - 3 R0cad^y ^y + O(s ), (130) g = d (1 - R ^yc^yd)+ O(s3). (131) ab ab 0c0d