⊦ as ⊆ as0 ↔ (∀ adr. adr ∈ as → adr ∈ as0)
∀ adr. adr ∈ ax.toSet → adr ∈ as ⊦ prefixn(n, ax).toSet ⊆ ax.toSet, prefixn(n, ax).toSet ⊆ as
Used terms: as, ax.toSet