1. Aarts, E., Lenstra, J.K. (eds.): Local Search in Combinatorial Optimization. Wiley, Chichester (1997)
2. Ahuja, R.K., Magnanti, T.L., Orlin, J.B.: Network Flows. Prentice Hall, Englewood Cliffs (1993)
3. Lecture Notes in Computer Science;K. Arata,2000
4. Bar-Ilan, J., Kortsarz, G., Peleg, D.: Generalized submodular cover problems and applications. In: The Israeli Symposium on the Theory of Computing, pp. 110–118 (1996) (also in Theoretical Computer Science, to appear)
5. Bartholdi, J.J., Orlin, J.B., Ratliff, H.D.: Cyclic scheduling via integer programs with circular ones. Operations Research 28, 110–118 (1980)