@article{TuGeZhangetal.2013,
  author    = {Rui Tu and Maorong Ge and Hongping Zhang and Guanwen Huang},
  title     = {The realization and convergence analysis of combined PPP based on raw observation},
  journal   = {Advances in space research},
  volume    = {52},
  number    = {1},
  pages     = {211 -- 221},
  doi       = {10.1016/j.asr.2013.03.005},
  year      = {2013},
}