@inproceedings{sgem2007paper,
  title = {GLOBAL IONOSPHERE MAPS OBTAINED FROM GLOBAL NAVIGATION SATELLITE SYSTEM (GNSS) DATA AND THEIR PERFORMANCE AFTER INTEGRATION OF SATELLITE ALTIMETRY MEASUREMENTS},
  author = {S. Todorova and H. Schuh},
  booktitle = {7th International Scientific Conference - SGEM2007},
  year = {2007},
  pages = {},
  publisher = {SGEM Scientific GeoConference},
  doi = {}
}