1. R. Castaing, Thesis, University of Paris, 1951.
2. R. Castaing and J. Descamp, J. Phys. Rad. 16, 304 (1955).
3. G. Shinoda, Optique des Rayons X et Microanalyse, Paris: Hermann. 1966. p. 97.
4. A. Vignes and G. Dez, Brit. J. Appl. Phys., Ser. 2, 1, 1309 (1968).
5. M. Green, Proc. Phys. Soc. 82, 204 (1963).