Romana, A. Geomagnetic data 1968 rapid variations A. Romana and D. Van Sabben - Paris International Union of Geodesy and Geophysics 1971 - vii+86p. - International Association of Geomagnetism and Aeronomy; No. 12w2 . Subjects--Topical Terms: Iaga Bulletin No.12w2Iaga Bulletin-dataIaga IndicesIugg Universal Decimal Class. No.: 550.38 / IAGA