Equation Icon  [ ] Ω⋅⋅⋅(x,x′)δ4(x, x′) = Ω ⋅⋅⋅δ4(x,x′), ( ) ( ′ ) (13.3 ) gαα′(x,x ′)δ4(x,x′) ;α = − ∂α′δ4(x,x′), gαα(x′,x)δ4(x,x′) ;α′ = − ∂αδ4(x,x′),