On the relation between activity-related frequency shifts and the sunspot distribution over the solar cycle 23Ângela R. G. Santos, Margarida S. Cunha, Pedro P. Avelino, William J. Chaplin and Tiago L. CampanteEPJ Web Conf., 160 (2017) 02013DOI: https://doi.org/10.1051/epjconf/201716002013