@article{Morel:6444,
      author        = "Morel, L  and Pottiaux, E. and Durand, F. and Follin,
                       J.-M. and Durand, S. and Van Baelen, J.",
      title         = "{Global validity and behaviour of tropospheric gradients
                       estimated by GPS}",
      month         = "Apr",
      year          = "2018",
}