1. Gamow, G. and Keller, G.: 1945,Rev. Mod. Phys. 17, 125.
2. Grabi?ska, T.: 1980, Lectures given at Schools of Methodology of Empirical Sciences (June and September), Technical University of Wroclaw.
3. Ikaunieks, J.: 1966, in J. Ikaunieks (ed.),Motions of Red Giant Stars, Publ. House ?Zinatne?, Riga (Academy of Science of the Latvian SSR).
4. Kaplan, S. A. and Shatsova, R. B.: 1975,Astron. Zh. 52, 260; interesting suggestions are contained in Zonn W. and Rudnicki, K.: 1959,Zvezdnaja Astronomija, Moskva Izdatelstvo Inostr. Lit.
5. Melik-Alaverdian, J. K.: 1978,Astroph. 14, 345 (Academy of Science of the Armenian SSR).