References
- L. Berwart, Bull. Soc. Roy. Sc. Liège, 36, 257 (1967).
- L. Berwart, Sc. Ind. Phot. (In press).
- M. Savelli, Pub. Sc. Univ. Alger., 4, 121 (1958) and 5, 5 (1959).
- R. C. Jones, J.O.S.A., 45, 799 (1955).
- L. Berwart, Bull. Soc. Roy. Sc. Liege, 34, 284 (1965).