1. K. Schwarzschild, B. Meyermann, A. Kohlschütter, O. Birck, Astronomische Mitteilungen der Universitaets-Sternwarte zu Goettingen 14, 1 (1910)
2. H. Rosenberg, Astronomische Nachrichten 193, 357 (1913)
3. J.A. Ambartsumian: Stellar Evolution and Astrophysics In: Acad. Sci. Armenian, Erevan, USSR, (1947)
4. D. Batchelor: Solar data at NSSDC. In: National Space Science Data Center NEWS (Volume 12, Number 3, 1996)
5. Exhibition http://www.dudleyobservatory.org/Exhibits/bessel.htm (The Dudley Observatory, Schenectady, NY 12308, 2003)