Usoskin, Ilya G.; Mursula, Kalevi; Arlt, Rainer; Kovaltsov, Gennady A. (2009). “A SOLAR CYCLE LOST IN 1793-1800: EARLY SUNSPOT OBSERVATIONS RESOLVE THE OLD MYSTERY”. The Astrophysical Journal700 (2): L154–L157. doi:10.1088/0004-637X/700/2/L154. ISSN0004-637X.
Tapping K.F. (1987). “Recent solar radio astronomy at centimeter wavelength: the temporal variability of the 10.7-cm flux”. J. Geophys. Res.92 (D1): 829–838. Bibcode: 1987JGR....92..829T. doi:10.1029/JD092iD01p00829.
Tapping K.F. (1987). “Recent solar radio astronomy at centimeter wavelength: the temporal variability of the 10.7-cm flux”. J. Geophys. Res.92 (D1): 829–838. Bibcode: 1987JGR....92..829T. doi:10.1029/JD092iD01p00829.
Usoskin, Ilya G.; Mursula, Kalevi; Arlt, Rainer; Kovaltsov, Gennady A. (2009). “A SOLAR CYCLE LOST IN 1793-1800: EARLY SUNSPOT OBSERVATIONS RESOLVE THE OLD MYSTERY”. The Astrophysical Journal700 (2): L154–L157. doi:10.1088/0004-637X/700/2/L154. ISSN0004-637X.