equation icon  n k2- n ab n \~/ Emn - 3 \~/ mr - emnas bH + 3Hmnw = 2 2 ( ) k--r- \~/ mr + k-- 2 \~/ mrE - 2QqEm - 3 \~/ npEmn + 3smnqEn - 9emnawnqEa . (131) 3 c 6