On the Structure of Sets in NP and Other Complexity Classes
Lawrence Landweber, Richard Lipton, Edward Robertson
1978
A simple technique is developed for manipulating the relative complexity of stes with respect to polynomial time reducibility. One application is the definition of a minimal pair (with respect to polynomial time reducibility) of sets in NP-P. The last section proves that the NP-complete are effectively enumerable while NP-P is not.