∀ m, n0. (m + n0) + n = m + n0 + n ⊦ (m + n0) + n = m + n0 + n
Used simplifier rules: add-rec: ⊦ m + n +1 = (m + n)+1;%inj-1: ⊦ n +1 = n0 +1 ↔ n = n0; from specification nat-basic1