s ⊆ s0 ++ a ⊦ a ∈ s0, a ∈ s, s ⊆ s0
Used simplifier rules: sub-ntrans: ⊦ s ⊆ s0 ∧ ¬ s ⊆ s1 → ¬ s0 ⊆ s1;%sub-add-01: ⊦ s ⊆ s ++ a;