1. On the relative complexity of subproblems of intractable problems;Ambos-Spies,1985
2. Beiträge zur Strukturtheorie von NP, Diplomarbeit;Braun,1983
3. The complexity of theorem proving procedures;Cook,1971
4. Computers and Intractability: A Guide to the Theory of NP-Completeness;Garey,1978
5. Algebras of feasible functions;Gurevich,1983