1. On the structure of combinatorial problems and structure preserving reductions;Ausiello,1977
2. Graphs and Hypergraphs;Berge,1973
3. The complexity of theorem-proving procedures;Cook,1971
4. Computers and Intractability: A Guide to the Theory of NP-Completeness;Garey,1978
5. Some simplified NP-complete graph problems;Garey;Theor. Comp. Sci.,1976