@article{MorfeldGronebergSpallek2014,
  author    = {Peter Morfeld and Jan David Alexander Groneberg and Michael Spallek},
  title     = {Effectiveness of low emission zones : large scale analysis of changes in environmental NO2, NO and NOx concentrations in 17 German cities},
  journal   = {PLoS One},
  volume    = {9},
  number    = {(8):e102999},
  doi       = {10.1371/journal.pone.0102999},
  year      = {2014},
}