equation icon  ab a b gd ' ab ' { ab g g ab } []G ± g'd'+ 2Rg d G ± g'd'= -4pd4(x, x )U g'd'+ d±(s) 2U g'd';gs + (s g- 4)U g'd' { ab g g ab ab a b gd } + d±(s) - 2V g'd';gs + (2 - s g)V g'd'+ []U g'd'+ 2R g d U g'd' { ab a b gd } + h±(- s) []V g'd'+ 2R g d V g'd'