@article{9648,
  author = {J. Mariska and Ludwig Oster},
  title = {Solar activity and the variations of the geomagnetic Kp-index},
  year = {1972},
  journal = {Solar Physics},
  volume = {26},
  pages = {241-249},
  month = {Jan-09-1972},
  issn = {0038-0938},
  doi = {10.1007/BF00155123},
}