⊦ as ⊆ as0 ↔ (∀ adr. adr ∈ as → adr ∈ as0)
⊦ (∀ adr. adr ∈ as → adr ∈ as0 ∩ as) ↔ as ⊆ as0
Used terms: as0 ∩ as, as