1. Worst-Case Analysis of a New Heuristic for the Travelling Salesman Problem;Christofides;Technical Report CMU,1976
2. Some NP-complete geometric problems;Garey,1976
3. Computers and Intractability: A Guide to the Theory of NP-Completeness;Garey,1979
4. Computational complexity and the travelling salesman problem;Johnson,1982
5. Worst-case analysis of heuristics;Johnson,1982