9Muhtarov G and Kutiev I. Autocorrelation method for temporal interpolation and short-term prediction of ionospheric data [J]. Radio Science, 1999, 34(2) : 459 -464.
10Hanbaba R. COST 251 final report, improved quality of service in ionospheric telecommunication systems planning and operation[J]. Warsaw: Space Research Centre, 1999, 127 - 142.