Research proof index

For a list φs = φ₀…φₙ of 𝓕.FieldOp, a Wick contraction φsΛ of φs, an element φ of 𝓕.FieldOp, a i ≤ φs.length and a k in φsΛ.uncontracted, then (φsΛ ↩Λ φ i (some k)).staticContract is equal to the product of - [anPart φ, φs[k]]ₛ if i ≤ k or [anPart φs[k], φ]ₛ if k < i - φsΛ.staticContract. The proof of this result ultimately...