Bartels, Julius Geomagnetic data 1958 rapid variations Julius Bartels, A. Romana and J. Veldkamp - Amsterdam International Union of Geodesy and Geophysics 1962 - vi+93p. - International Association of Geomagnetism and Aeronomy; No. 12m2 . Subjects--Topical Terms: Iaga Bulletin No.12m2Iaga Bulletin-dataIaga IndicesIugg Universal Decimal Class. No.: 550.38 / IAGA