⊦ s ≠ ∅ ∧ s ⊆ s0 → s.min ∈ s0
Used simplifier rules: ⊦ s -- a = ∅ ↔ s = ∅ ∨ s = ∅ ++ a; (ws)% ⊦ s -- a ⊆ s; (s) Used terms: s, s -- s.min