a ∈ st, ∀ a. a ∈ st → a ∈ st0 ∧ st[a] = st0[a], ∀ a. a ∈ st0 → a ∈ st1 ∧ st0[a] = st1[a] ⊦ a ∈ st1 ∧ st[a] = st1[a]
Used simplifier rules: Subset: ⊦ st1 ⊆ st2 ↔ (∀ a. a ∈ st1 → a ∈ st2 ∧ st1[a] = st2[a]);