Equation Icon  ( ) G+n [g;x, y) ≡ ⟨0|φˆn [g; x)ˆφn[g;y)|0⟩, iGFn [g; x,y) ≡ ⟨0|T ˆφn[g;x)φˆn [g;y ) |0⟩. (44 )