Equation Icon  ⟨ ⟩ ΔX--(n1,-r,t)-ΔX--(n2,r,t) ∑ 2-ℓ +-1 (XX ) X X = 4π Cℓ (z )P ℓ(n1 ⋅ n2). (224 ) 0 0 ℓ