1. N. Alon, J.H. Spenser, The Probabilistic Method, Wiley, New York, 1992.
2. S. Arora, C. Lund, Hardness of approximations, in: D. Hochbaum (Ed.), Approximation algorithms for NP-hard Problems, PWS Publishing Company, New York, 1997, pp. 399–446.
3. Location of bank accounts to optimize float: an analytic study of exact and approximate algorithms;Cornuejols;Management Sci.,1977
4. On the uncapacitated location problem;Cornuejols;Ann. Discrete Math.,1977
5. G. Cornuejols, G.L. Nemhauser, L.A. Wolsey, The uncapacitated facility location problem, in: P.B. Mirchandani, R.L. Francis (Eds.), Discrete Location Theory, Wiley, New York, 1990, pp. 119–171.