1. Corbin, T. 1978, in IAU Symposium 109, Modern Astrometry, ed. F. Prochazka and R. Tucker, Vienna, p. 505.
2. Corbin, T., Smith, D. and Carpenter, M. 1975, Bull. Am. Astron. Soc.
9, 597.
3. de Vegt, C. 1978, in IAU Symposium 109. Modern Astrometry. ed. F. Prochazka and R. Tucker, Vienna, p. 527.
4. Guenther, A. and Kox, H. 1970, Astron. Astrophys., 4, 156.
5. Guenther, A. and Kox, H. 1971, Astron. Astrophys., 12, 175.