Aardmagnetisme en poollicht / door J. VeldkampDayside and polar cap aurora / by Per Even Sandholt, Herbert C. Carlson and Alv EgelandDayside and polar cap aurora / by Per Even Sandholt, Herbert C. Carlson, and Alv EgelandAardmagnetisme en poollicht / door J. VeldkampAurora / by Alister Vallance JonesPolar and magnetospheric substorms / Syun-Ichi Akasofu