⊦ st1 ⊆ st2 ↔ (∀ a. a ∈ st1 → a ∈ st2 ∧ st1[a] = st2[a])
∀ a. a ∈ st → a ∈ st0 ∧ st[a] = st0[a] ⊦ ∀ a0. a0 ∈ st -- a → a0 ∈ st0 ∧ (st -- a)[a0] = st0[a0]
Used terms: st0, st -- a