Equation Icon  a2(E α) = αab2ulk(E ) + (1 − α)aΣ2 + O (1 − α)2, aΣ = Aa Σ+ Ba Σ, 2 ∫A B aΣA = π- (Rijij − 2Rii + R ), 8 Σ∫ Σ π- 1- aB = − 8 Σ(Rijij − Rii + 3R ), (276 )