1. Alcock, Ch. and Paczynski, B.: 1978,Astrophys. J. 223, 244.
2. Allen, C. W.: 1955, inAstrophysical Quantities, Univ. of London, p. 209.
3. Allen, C. W.: 1963, inAstrophysical Quantities, Univ. of London, p. 199.
4. Allen, C. W.: 1973, inAstrophysical Quantities, Univ. of London, p. 200.
5. Anthony-Twarog, B. J. and Demarque, P.: 1977,Astron. Astrophys. 57, 471.