@article{Cliver:1452,
      author        = "Cliver, E.W. and Clette, F. and Svalgaard, L. and Vaquero,
                       J.M.",
      title         = "{Recalibrating the Sunspot Number (SN): The 3rd and 4th SN
                       Workshops}",
      year          = "2015",
}