Equation Icon  A −A -1 -1 ∂μe e = ∂ μA + 2![A, ∂μA ] + 3![A,[A, ∂μA ]] + ⋅⋅⋅ , A −A 1 (9.60 ) e Be = B + [A,B ] + 2![A, [A,B ]] + ⋅⋅⋅ .