1. Barstow, M., et al., 1993, in White Dwarfs: Advances in Observation and Theory, M.A. Barstow ed., NATO ASI C Vol 403, Kluwer, p. 433.
2. Bergeron, P. 1988, Ph.D. Thesis, Universite de Montreal.
3. Bergeron, P., Saumon, D., and Wesemael, F. 1995, ApJ (in press).
4. Claver, C.F., and Winget, D.E. 1995, this volume.
5. Eggen, O.J., and Greenstein, J.L. 1965, ApJ, 141, 83.