1. Ake, T.B. 1979, Ap. J., 234, 538.
2. Auman, J.R., and Woodrow, J.E.J. 1975, Ap. J., 197, 163.
3. Becker, S.A., and Iben, I. 1979, Ap. J., 237, 111.
4. Bidelman, W.P. 1956, in Vistas in Astronomy, vol. 2, ed. A. Beer ( New York: Perganon Press ), p. 1428.
5. Blanco, B.M., Blanco, V.M., and McCarthy, M.F. 1978, Nature, 271, 638.