1. Beatty, J. Kelly and Goldman, S. J.: 1994,Sky & Telescope October, 18.
2. Bill, Christian: 1991,CCD Astronomy, pp. 205–209.
3. Coggins, J. M., Fullton, L. K., and Carney, B. W.: 1994,The Restoration of HST and Spectra II, Space Telescope Science Institute, pp. 24–39.
4. Eicher, D. J.: 1994;Astronomy August, 72.
5. Karkoschka, E.: 1994;Icarus 111, 174–192.