523 20160222141717.0 10.1007/s11207-012-0184-5 DOI SIDCimport-603 Lefèvre, L. 2014 Survey and Merging of Sunspot Catalogs STCE Clette, F. Solar Physics 289 2014 545-561 http://download.springer.com/static/pdf/520/art%253A10.1007%252Fs11207-012-0184-5.pdf?auth66=1427274035_a58dd3c090a59cdd9fbeba5106033522=.pdf published in REFERD