Geomagnetic data indices K and C 1956 /
by J. Bartels, A. Romana and J. Veldkamp
- Amsterdam : North-Holland, 1959
- ix, 157 p. : ill. ; 24 cm.
- International association of geomagnetism and aeronomy bulletin ; no. 12 K .
International association of geomagnetism and aeronomy formaly known as association of terrestrail magnetism and electricity