| bst(t), b ∈ t, b < t .leftmost ⊦ b = t .leftmost, t = leaf |
bst(t) ∧ b ∈ t ∧ b < t .leftmost, ∀ t0, b. # t0 < # t → (bst(t0) ∧ b ∈ t0 ∧ b < t0 .leftmost → b = t0 .leftmost ∨ t0 = leaf) ⊦ b = t .leftmost ∨ t = leaf
[[CONCRETESIMPRULES : ([CSIMPLESSPRED : <])], [EXTRATERMS : (# t)]]