Huang, X. and Reinisch, B.W.: Vertical electron content from ionograms in real time, Radio Science, 36, 2, 335-342, 2001. (Pubitemid 32432672)
Leitinger, R., Radicella, S., and Nava, B.: Electron density models for assessment studies-new developments, Acta Geodet. Geophys. Hung. 37, 183-193, 2002. (Pubitemid 35003208)
Warnant, R. and Jodogne, J.-C.: A comparison between TEC computed using GPS and Ionosonde measurements, Acta Geodet. Geophys. Hung. 33, 147-153, 1998. (Pubitemid 128463952)