@article{Mathieu:5688,
      author        = "Mathieu, Sophie and Lefèvre, Laure  and von Sachs, Rainer
                        and Delouille, Veronique  and Ritter, Christian  and
                       Clette, Frédéric ",
      title         = "{Nonparametric monitoring of sunspot number observations.
                       }",
      year          = "2022",
}