References
- Lehmann, E., and Tausch E., Phot, Korr., 71, 17, 1935.
- Axford, A. J. and Kendall, J. D., J. Phot, Sci., 2, No. 1. 1-7, 1954.
- Levenson. G. I. P., Phot., J., 89H, 13, 1949.
- James, T. H., Pros. R.P.S. Cent. Conf., London. I953.
- Axford. A. J., and Kendall. J. D., Brit, J. Photo., June 8th. 1956.