equation icon  [ a a2 c d 3 ] gtt = - 1 + 2aa^x + (aa^x ) + R0c0d^x ^x + O(s ) , (125) 2 c d 3 gta = - 3R0cadx^x^ + O(s ), (126) 1 gab = dab- -Racbd^xc^xd + O(s3). (127) 3