| ∀ b, a. (st0 -- b)[a] = st0[a] ∨ a = b ⊦ (st0[a0, d] -- b)[a] = st0[a], a = a0, a = b |
⊦ a ≠ b → st[b, d] -- a = (st -- a)[b, d]
b = a0, ∀ b, a. (st0 -- b)[a] = st0[a] ∨ a = b ⊦ (st0[a0, d] -- b)[a] = st0[a], a = b, a = a0
∀ b, a. (st0 -- b)[a] = st0[a] ∨ a = b ⊦ (st0 -- b)[a0, d][a] = st0[a], a = b, a = a0, b = a0
Used terms: b, d, a0, st0