1. V. A. Marsakov and A. A. Suchkov, Astron. Zh. 54, 1232 (1977) [Sov. Astron. 21, 700 (1977)].
2. R. Zinn, Astrophys. J. 293, 424 (1985).
3. R. Zinn, in The Globular Cluster-Galaxy Connection, Ed. by H. Smith and J. Brodee, ASP Conf. Ser. 48, 38 (1993).
4. G. S. Da Costa and T. F. Armandroff, Astron. J. 109, 2533 (1995).
5. W. E. Harris, Astron. J. 112, 1487 (1996).