⊦ ns = ns0 ↔ (∀ n. n ∈ ns ↔ n ∈ ns0)
Used simplifier rules: elems-def: ⊦ n ∈ elems nx ↔ n ∈ nx;% ⊦ ¬ n ∈ []; (s)% ⊦ ¬ n ∈ ∅; (s) Used terms: ∅, elems []