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2. International Reference Ionosphere;Bilitza;NSSDC/WDCA-R&S 90-22,1990
3. PRIME (Prediction and Retrospective Ionospheric Modelling over Europe);Bradley,1995
4. EISCAT Catalogue specification of the ionospheric quiet and disturbed conditions;Gulyaeva;Adv. Space. Res.,1995
5. Enhanced variability in the topside ionosphere;Gulyaeva;Annali di Geofisica,1995