1. BAUM, W. A., and DUNKELMAN, L. (1950) J. opt. Soc. Amer., 40, 782
2. Arch;BURNS, R.P.;Ophthal. (Chicago),1965
3. CLEASBY, G. W. (1970) Ibid., 83, 145
4. DE GUILLEBON, H., PFISTER, R., GOVIGNON,J., POMERANTZEFF, o., and SCHEPENS, C. (1971) Ibid., 85, 7I2
5. GEERAETS, W. J., WILLIAMS, R. C., HAM, W. T., and GUERRY, D. (1962) Ibid., 68, 58