2Huang H.C,Li R. A k-product uncapacitated facility location problem[J].European Journal of Operational Research,2007.
3Fisher, M.L,Nemhauser, G.L,Wolsey, L.A. An analysis of approximation for maximizing submodular set functions-II[J].Mathematical Programming Study,1978.73-87.
4Bumb A.F,Kern W. A simple dual ascent algorithm for the multilevel facility location problem[A].2001.55-62.
5Klincewicz, J.G,Luss, H. A dual based algorithm for multiproduct uncapacitated facility location[J].Transportation Science,1987.198-206.
4Aardal K,Chudak F A,Shmoys D B.A 3-approximation algorithm for the k-level uncapacitated facility location problem[J].Information Processing Letters,1999,72:161-167.
5Ageev A.Improved approximation algorithms for multilevel facility location problems[J].Operations Research Letters,2002,30:327-332.
6Ageev A,Ye Yinyu,Zhang Jiawei.Improved combinatorial approximation algorithms for the k-level facility location problem[J].SIAM Journal on Discrete Mathematics,2004,18(1):207-217.
7Bumb A F,Kern W.A simple dual ascent algorithm for the multilevel facility location problem[C]//LNCS 2129:4th International Workshop on Approximation Algorithms for Combinatorial Optimization Problems,2001:55-62.
8Chudak F A,Shmoys D B.Improved approximation algorithms for the uncapacitated facility location problem[J].SIAM Journal on Computing,2003,33:1-25.
9Guha S,Khuller S.Greedy strikes back:improved facility location algorithms[J].Journal of Algorithm,1999,31:228-248.
10Huang H C,Li R.A k-product uncapacitated facility location problem[J].European Journal of Operations Research,2007.