@ARTICLE{varshavsky2007gsm,
  author    = "Alex Varshavsky and Eyal de~Lara and Anthony LaMarca and Jeffrey Hightower and Veljo Otsason",
  title     = "GSM Indoor Localization",
  journal   = "Pervasive and Mobile Computing Journal",
  publisher = "Elsevier",
  volume    = "3",
  number    = "6",
  pages     = "698--720",
  year      = "2007"
}