1. The solar constant of radiation;Abbot;Proc. Am. Philos. Soc.,1911
2. ASTM, 1974. Standard specifications for solar constant and air mass zero solar spectral irradiance. Standard E490-73a, ASTM International.
3. ASTM, 2000. Solar Constant and Zero Air Mass Solar Spectral Irradiance Tables. Standard E490-00, ASTM International.
4. Solar variability due to sunspots and faculae;Chapman;J. Geophys. Res.,1987
5. The New Sunspot Number: assembling all corrections;Clette;Solar Phys.,2016