−iMe−e−=−i(e2(p∗1+p′∗1)μ(p∗2+p′∗2)μ(p′∗2−p∗2)2−e2(p∗1+p′∗2)μ(p∗2+p′∗1)μ(p′∗1−p∗2)2)
Me−e−=e2(P∗1P∗2+P′∗1P′∗2+P′∗1P∗2+P∗1P′∗2(P′∗2−P∗2)2−P∗1P∗2+P′∗2P′∗1+P′∗2P∗2+P∗1P∗1(P∗1−P∗2)2)
Using the fact that \mathbf P_1^{'*} \mathbf P_2^{'*}=\mathbf P_1^* \mathbf P_2^* \quad & \quad \mathbf P_1^{'*} \mathbf P_1^{*}=\mathbf P_2^{'*} \mathbf P_2^* \quad & \quad \mathbf P_1^{*}
\mathbf P_2^{'*}=\mathbf P_2^* \mathbf P_1^{'*}
Me−e−=e2(2P∗1P∗2+2P′∗1P∗2(P′∗2−P∗2)2−2P∗1P∗2+2P∗1P′∗1(P′∗1−P′∗2)2)
Me−e−=e2((P∗21−2P∗1P′∗2+P′∗22)−(P∗21+2P∗1P∗2+P∗22)t−(P∗21−2P∗1P′∗1+P′∗21)−(P∗21+2P∗1P∗2+P∗22)u)
Me−e−=e2(u−st+t−su)