@article{TuZhangGeetal.2013,
  author    = {Rui Tu and Hongping Zhang and Maorong Ge and Guanwen Huang},
  title     = {A real-time ionospheric model based on GNSS Precise Point Positioning},
  journal   = {Advances in space research},
  volume    = {52},
  number    = {6},
  pages     = {1125 -- 1134},
  doi       = {10.1016/j.asr.2013.06.015},
  year      = {2013},
}