1. Allen, C. W. 1973,Astrophysical Quantities, 3 edn, Athlone Press, London, p. 206.
2. Bassett, E. E. 1978,Observatory,98, 122.
3. Beavers, W. I., Griffin, R. F. 1979,Publ. astr. Soc. Pacific,91, 521.
4. Griffin, R. F. 1967,Astrophys. J.,148, 465.
5. Griffin, R. F. 1979,Observatory,99, 1.