| Φ Φ α α k [ k + 1.. N ] ⟩ ⟩ = ∑ ∑ α α k + 1 , α α k + 2 . . α α N Γ Γ α α k α α k + 1 [ k + 1 ] i k + 1 λ λ α α k + 1 [ k + 1 ] ⋅ ⋅ ⋅ ⋅ λ λ α α N − − 1 N − − 1 Γ Γ α α N − − 1 [ N ] i N | i k + 1 i k + 2 . . i N ⟩ ⟩