2S. A. Cook. The complexity of theorem proving proceduresfj]. Proc. 3rd ACM Symp. On the Theory of Computing, ACM, 1971, 1514-158.
3R. M. Karp. On the complexity of combinatorial problems[J]. Networks, 1975, 45-68.
4N. Christofides. Worscase analysis of a new heuristic for the traveling salesman problem[R]. Technical Report, Graduate School ofIndustrial Administration, Camegie-Melon University, Pittsburgh, PA 1976.
5L. G. Khachiyan. A polynomial algorithm in linear programming[J]. Soviet Math. Dokl.,1979,191-194.
6Shoshani A. Statistical databases: characteristics, problems, and some solutions. In: Proceedings of the 8th Interna- tional Conference on Very Large Data Bases, Mexico City, 1982. 208-222.
7Shoshani A, Olken F, Wong H K T. Characteristics of scientific databases. In: Proceedings of the 10th International Conference on Very Large Data Bases, Singapore, 1984. 147-160.
8Shoshani A, Wong H K T. Statistical and scientific database issues. IEEE T~'ans Softw Eng, 1985, 11:1040-1047.
9Turing A M. On computable numbers, with an application to the entscheidungs problem. Proc London Math Soc, 1936, 2:230-265.
