1. Aaronson, M. et al. 1982, Ap. J. Suppl, 50, 241.
2. Allen, R. J., Baldwin, J. E. and Sancisi, R. 1978, Astr. Ap., 62, 397.
3. Bartel, N. 1985, in Supernovae as Distance Indicators, Lecture Notes in Physics, ed. N. Bartel (Springer-Verlag, Berlin), 224, 107.
4. Bartel, N. 1986, in Highlights of Astronomy, ed. J. P. Swings, 7, 655.
5. Bartel, N., Herring, T. A., Ratner, M. I., Shapiro, I. I., and Corey, B. E. 1986, Nature, 319, 733.