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