1. Carrington, R.C.: Observations of the Spots on the Sun from November 9, 1853 to March 24, 1861 Made at Redhill, London. Williams and Norgate, Edinburgh (1863)
2. Teague, E.T.H.: J. Br. Astron. Assoc. 106, 2 (1996)
3. Thompson, W.T.: A&A 449, 791 (2006)
4. Sanchez-Bajo, F., Vaquero, J.M.: Eur. J. Phys. 34, 527 (2013)
5. Meadows, P.: J. Br. Astron. Assoc. 112, 6 (2002)