@article{MatzkaStolleYamazakietal.2021,
  author    = {J{\"u}rgen Matzka and Claudia Stolle and Yosuke Yamazaki and Oliver Bronkalla and Achim Morschhauser},
  title     = {The geomagnetic Kp index and derived indices of geomagnetic activity},
  journal   = {Space weather : the international journal of research and applications},
  volume    = {19},
  number    = {5},
  doi       = {10.1029/2020SW002641},
  year      = {2021},
}