∀ {σ : Type u_1} {m : MonomialOrder σ} {R : Type u_2} [inst : CommRing R] [NoZeroDivisors R]
  (p₁ p₂ q₁ q₂ : MvPolynomial σ R),
  m.sPolynomial (m.leadingTerm p₁ * q₁) (m.leadingTerm p₂ * q₂) =
    (MvPolynomial.monomial (m.degree (p₁ * q₁) ⊔ m.degree (p₂ * q₂) - m.degree q₁ ⊔ m.degree q₂))
        (m.leadingCoeff p₁ * m.leadingCoeff p₂) *
      m.sPolynomial q₁ q₂