TY - JOUR A1 - Schreiber, H. T1 - On the periodic variations of geomagnetic activity indices Ap and ap JO - Ann. Geophys. J1 - ANGEO VL - 16 IS - 5 SP - 510 EP - 517 Y1 - 1998/05/31 PB - Springer Verlag SN - 1432-0576 UR - https://angeo.copernicus.org/articles/16/510/1998/ L1 - https://angeo.copernicus.org/articles/16/510/1998/angeo-16-510-1998.pdf DO - 10.1007/s00585-998-0510-2 ER -