1. Aime, C., Demarcq, J., Fossat, E., Ricort, G.: Nouv. Rev. Opt. 5 (1974) 257.
2. Anon.: Kitt Peak National Observatory Facilities Book, Kitt Peak National Observatory, Tucson (1977).
3. Anon.: Sacramento Peak Observatory Users Manual, Sacramento Peak Observatory, Sunspot (1978).
4. Bahner, K.: Landolt-Börnstein, NS, Vol. VI/1 (1965) p. 14.
5. Bappu, M.K.V.: Sol. Phys. 1 (1967) 151.