1. Ionospheric Radio
2. Modell-parameter für den electroneninhalt der ionosphare in mittleren breiten;Feitchter;Kleinheubach. Ber.,1989
3. Ionospheric time delay algorithm for single frequency GPS users;Klobuchar;IEEE, Aerosp. Electron. Syst.,1987
4. A harmonic analysis of ATS-6 electron content observations at Lancaster, U.K., during 1975-1976;Poulter;Ann. Geophys.,1981