⊦ σ = σ2 ↔ # σ = # σ2 ∧ (∀ n. ⌜n⌝ < # σ → σ[n] = σ2[n])
# σ0 = ∞, (σ0 to n) + σ1 = σ0 ⊦ # σ1 = #(σ0 from n) ∧ (∀ n0. ⌜n0⌝ < # σ1 → σ1[n0] = (σ0 from n)[n0])
Used terms: σ0 from n, σ1