equation icon  [ ] tr V (a1)Gbmn V (1)Gbrs = integral b integral n n ' a b ' -dnk---dnq-- ik(x-x') ~ b ~b mn,ab d x d x hmn(x)h ab(x ) (2p)n (2p)n e G mn(k + q)G rs(q)T (q,k), (170)