@article{Veronig:6014,
      author        = "Veronig, A. M. and Jain, S. and Podladchikova, T. and
                       Poetzi, W. and Clette, F.",
      title         = "{Hemispheric Sunspot Numbers 1874-2020 (VizieR Online Data
                       Catalog)}",
      year          = "2021",
}