S. Johnson introduced the concept of Turing reduction and by using this concept intended to make the theory of NP-completeness applicable to an extended class of problems including the combinatorial optimal problems in [3].

• S.；Johnson在[3]中引入“图灵归约”的概念；利用这个概念把NP完全性理论推广到包括组合最优化问题在内的更广的一类问题上。