Equation Icon  ∮ ′ ′ [( ) ( ) ( ) ( ) ] ∮ γ¯A B ΔA ′A λA ΔB ′B μB + 𝒯A ′CDE λE 𝒯B′CDF μF d𝒮 = − i2 λAμBFABcd, (4.5 ) 𝒮 𝒮