@article{DBLP:journals/ipl/AardalCS99,
  author    = {Karen Aardal and
               Fabi{\'a}n A. Chudak and
               David B. Shmoys},
  title     = {A 3-Approximation Algorithm for the k-Level Uncapacitated
               Facility Location Problem},
  journal   = {Inf. Process. Lett.},
  volume    = {72},
  number    = {5-6},
  year      = {1999},
  pages     = {161-167},
  ee        = {http://dx.doi.org/10.1016/S0020-0190(99)00144-1},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}