1. Abetti, G. and Novakova, B.: 1929,Oss. Astrofis. Arcetri Contr. No. 46, 25.
2. Adams, W. S.: 1911,Carnegie Inst. of Washington Publ. No. 138.
3. Aslanov, I. A.: 1963,Astron. Zh. 40, 1036 (Soviet Astron.-AJ. 7, 794).
4. d'Azambuja, L., Mr. and Mrs.: 1948,Ann. Obs. Paris 6, part 7.
5. De Jager, C.: 1959,Handbuch der Physik (Ed. by S. Flügge), Springer-Verlag, Berlin.